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 X' /■,  /,;..  I  /„„ ;  /,  „t  a;,,,,.- 

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«V  , . « . S.'il/wA-s  /'/iiffc/i  lWa''Cf 
lO  I'artAtr/uvi  at  / 

J 'J  '/im/'/f  im  tlif   llijius  at.-flAms 

N  A'tfv/ttiti/t  OZ/riiek  lif/ore. 

1 7f'Kffj-  at  /*tsa 
,  ^trf/f/f  f/ '  S//'a,t//t/r^  fa//tf//rf// 
Sirr/t/r  ,>/',Ui/,ui  fMii-Jra/ 
tW/ff/o/  a/  U'aj/tt/ti//i'n 

rni/nf  Sf,it,s  MMii  J'/„7,it/f^,/u„ 
Balt/f  Moiumifiit  ,JI,i/4inliitv 


ELEMENTS 


OF 

TECHNOLOGY, 

TAKEN  CHIEFLY  FROM 

A  COURSE  OF  LECTURES 

DELIVERED 

AT  CAMBRIDGE, 

ON  THE 

APPLICATION  OF  THE  SCIENCES 

,  TO  THE 

USEFUL  ARTS. 

NOW  PUBLISHED 

FOR  THE  USE  OF  SEMINARIES  AND  STUDENTS. 


BY  JACOB  BIGELOW,  M.  D. 

Professor  of  Materia  Medica,  and  late  Rumford  Piofesi3or  in  Harvard  University  ;  Correspond- 
ing Secretary  of  the  American  Academy  of  Arts  and  Sciences ;  Member  of  tiie  American 
Philosophical  Society  ;  of  the  Linnaean  Societies  of  London  and  Paris,  &c. 


BOSTON. 

BILLIARD,  GRAY,  LITTLE,  AND  WILKINS. 


1829. 


DISTRICT  OF  RLVSSACHUSETTS,  TO  WIT: 

District  Clerk^s  Office. 
Be  it  remembered,  that  on  the  ninth  day  of  July,  A.  D.  1829,  in  the  fiftyfourth  year  of  the 
Ind(;|)cii(leiice  of  the  Uiiileii  States  of  America,  Jacob  Bigelow,  of  the  said  district,  has  deposit- 
ed ill  this  olfice  the  title  of  a  book,  the  right  whereof  he  claims  as  Author,  in  the  worda 
following,  lo  wit : 

'  Elements  of  Teclinology,  taken  chiefly  from  a  Course  of  Lectures  delivered  at  Cambridge, 
on  the  Application  of  the  acionces  to  the  Usaful  Arts.  Now  puhlishe;!  for  the  Use  of  Semi- 
naries aii.i  SiuJents  By  Jacob  Bigei.iw,  M.  D.,  Professor  of  Materia  Modica,  and  late 
Kuinford  Piofessor  in  Harvard  (J.iiversiiy  5  Cjriesp,):i  ii;ig  Secri'tary  of  the  American 
Academy  of  Arts  and  Scie  ices ;  Memljer  of  the  American  Philosophical  Society  ;  of  the 
Liniiae.iii  Societies  of  London  and  I'aiis,  &.c  ' 

Ir  conformity  to  the  act  of  the  ("ongrf^ss  of  the  United  States,  entitled  '  An  act  for  the  en- 
CourHgeiiieiU  of  leaniiiig,  by  securing  the  copies  of  iiiap^^,  charts,  and  hooks,  to  the  authors 
an  I  propri.'tors  of  such  copie-;,  diiriiig  the  tinr's  llierinii  inoiitionod  ; '  and  also  to  an  act, 
eiJtiilo.l  '  An  act  supplenidiitary  to  an  act,  ealitlu.l,  "  An  act  for  the  encouragement  of 
learni  ig,  by  securing  the  copies  of  maps,  charts,  and  books,  to  the  anlh.irs  and  |)roprietor3 
of  such  copies,  dui  i  ig  the  times  therein  .iicMitioiK!'!  •,  "  and  extending  the  beuetits  thereof  to 
the  arts  of  designing,  engraving,  aud  etching  historical  and  other  prints.' 

J  NO.  W  DAVIS, 
Clerk  of  the  District  of  Jilassachusetts. 


EXAMINER   PRESS  SCHOOL  STREET. 


ADVEll  TISEiVIEIVT. 


A  COURSE  of  Lectures  on  most  of  the  subjects  which  occupy 
this  volume,  has  been  delivered  at  Cambridge,  during  ten  years 
past,  in  pursuance  of  the  will  of  the  late  Count  Rumford,  by 
whose  bequest  a  professorship  is  founded  in  Harvard  University, 
on  the  Application  of  the  Sciences  to  the  Useful  Arts.  Parts 
of  the  same  course  have  been  repeated  in  Boston,  to  large 
audiences. 

The  degree  of  interest  which  has  been  taken  in  these 
Lectures,  has  led  me  to  believe  that  the  subject  is,  in  itself, 
peculiarly  capable  of  exciting  the  attention  and  curiosity  of 
students.  There  can  be  no  doubt  that  the  knowledge,  which 
this  study  is  intended  to  furnish,  is  of  great  use  in  the  common 
affairs  of  life  ;  and  probably  its  advancement  has  contributed 
more  than  that  of  any  other  science,  to  the  improved  condition 
of  the  present  age. 

A  certain  degree  of  acquaintance  with  the  theory  and 
scientific  principles  of  the  common  arts,  is  found  so  generally 
important,  that  most  educated  men,  in  the  course  of  an  ordinary 
practical  life,  are  obliged  to  obtain  it  from  some  source,  or  to 
suffer  inconvenience  for  the  want  of  it.  He  who  builds  a 
house,  or  buys  an  estate,  if  he  would  avoid  disappointment  and 
loss,  must  know  something  of  the  arts,  which  render  them 


IV 


ADVKHTISEMENT. 


appropriate,  and  tenantable.  He  who  travels  abroad  to  instruct 
himself,  or  enlighten  his  countrymen,  finds  in  the  works  of  art, 
the  most  commanding  objects  of  his  attention  and  interest. 
He  who  remains  at  home,  and  limits  his  ambition  to  the  more 
humble  object  of  keeping  his  apartment  warm,  and  himself 
comfortable,  can  only  succeed  through  the  instrumentality  of 
the  arts. 

There  has  probably  never  been  an  age  in  which  the  practical 
applications  of  science  have  employed  so  large  a  portion  of  the 
talent  and  enterprise  of  the  community,  as  in  the  present ;  nor 
one  in  which  their  cultivation  has  yielded  such  abundant 
rewards.  And  it  is  not  the  least  of  the  distinctions  of  our  own 
country,  to  have  contributed  to  the  advancement  of  this  branch 
of  improvement,  by  many  splendid  instances  of  inventive 
genius,  and  successful  perseverance. 

The  importance  of  the  subject,  and  the  prevailing  interest, 
which  exists  in  regard  to  the  arts  and  their  practical  influences, 
appear  to  me  to  have  created  a  want,  not  yet  provided  for,  in 
our  courses  of  elementary  education.  Information  on  these 
subjects  is  scattered  through  the  larger  works  on  mechanics, 
on  chemistry,  mineralogy,  engineering,  architecture,  domestic 
economy,  the  fine  arts,  &c.,  so  that  it  rarely  happens,  that  a 
student  in  any  of  our  colleges,  gathers  information  enough  to 
understand  the  common  technical  terms  which  he  meets  with 
in  a  modern  book  of  travels,  or  periodical  work.  It  is  only  by 
making  the  elements  of  the  arts  themselves,  subjects  of  direct 
attention,  that  this  deficiency  is  likely  to  be  supplied. 

To  embody,  as  far  as  possible,  the  various  topics  which 
belong  to  such  an  undertaking,  I  have  adopted  the  general 
name  of  Technology,  a  word  sufficiently  expressive,  which  is 
found  in  some  of  the  older  dictionaries,  and  is  beginning  to  be 
revived  in  the  literature  of  practical  men  at  the  present  day. 


ADVERTISEMENT. 


r 


Under  this  title  it  is  attempted  to  include  such  an  account  as 
the  limits  of  the  volume  permit,  of  the  principles,  processes, 
and  nomenclatures  of  the  more  conspicuous  arts,  particularly 
those  which  involve  applications  of  science,  and  which  may  be 
considered  useful,  by  promoting  the  benefit  of  society  together 
with  the  emolument  of  those  who  pursue  them. 

In  preparing  for  the  press  the  lectures  on  which  this  work  is 
founded,  some  variations  from  the  original  form  have  been  made, 
together  with  such  additions  as  my  leisure  from  professional 
engagements  has  permitted.  In  doing  this,  occasional  use 
has  been  made  of  the  works  of  Robison,  Young,  Tredgold, 
and  several  of  the  late  chemical  writers.  But  as  the  present 
elementary  volume  is  composed  for  the  instruction  of  the 
uninitiated,  rather  than  for  the  perfection  of  adepts,  it  has  been 
found  necessary  to  condense  and  to  endeavor  to  render 
intelligible  the  subjects  of  consideration,  rather  than  to  dilate 
them  by  minute  expositions  and  details.  For  the  use  of  those 
students,  who  may  wish  to  extend  their  inquiries  in  reference 
to  any  of  the  particular  subjects,  a  list  of  some  of  the  more 
prominent  authors,  and  works  of  value,  that  treat  upon  the 
several  subjects,  is  subjoined  at  the  end  of  each  chapter. 
Among  some  of  these  works,  the  authorities  for  the  facts  stated 
in  the  preceding  chapters,  will  in  most  instances  be  found. 

For  the  convenience  of  seminaries  which  may  make  use  of 
this  work,  the  wood  cuts  and  diagrams  which  are  interspersed 
with  the  text,  are  reprinted  at  the  end  of  the  volume. 

BOSTON,  JULY   1829.  J.  B. 


CORRECTIONS. 


Page    16,  line  3,  for  corbonate,  read  carbonate. 

"  125,  "  10  from  bottom,  for  120,  read  148.  The  height  of  the  dome  of 
the  Capitol.  This  1  am  informed  by  Mr  Buifinch  the  architect, 
is  the  actual  height,  though  it  is  differently  stated  in  books. 

"    127,    "    1,  for  will,  read  may. 

"    206,    "    3,  for  pieces,  read  piers. 

"   292,  bottom  line,  for  excentric,  read  eccentric. 


CONTENTS. 


CHAPTER  I. 

Of  the  Materials  used  in  the  Arts. 

Materials  from  the  Mineral  Kingdom,  Stones  and  Earths,  Marble, 
page  7.  Granite,  8.  Sienite,  9.  Freestone,  Slate,  Soapstone,  10.  Ser- 
pentine, Gypsum,  Alabaster,  11.  Challi,  Fluor  Spar,  Flint,  Porphyry,  12. 
Buhrstone,  Novaculite,  Precious  Stones,  Emery,  13.  Sand,  Pumice,  Tripoli, 
Clay,  14.  Asbestus,  CVmenfs,  Limestone,  15.  Puzzolana,  16.  Tarras,  Other 
Cements,  17.  Maltha,  18.  jT/e/aZs,  Iron,  Copper,  19.  Lead,  tin,  20.  Mercury, 
Gold,  Silver,  21.  Platinum,  Zinc,  Antimony,  Bismuth,  Arsenic,  Manganese, 
22.  Combustibles,  &c.,  Bitumen,  Amber,  Coal,  Anthracite,  23.  Graphite, 
Peat,  Sulphur,  24.  Materials  from  the  Vegetable  Kingdom,  Wood,  Bark, 
Oak,  25.  Hickory,  Ash,  Elm,  Locust,  26.  Wild  Cheny,  Chesnut,  Beech, 
Basswood,  Tulip  Tree,  27.  Maple,  Birch,  Button  Wood,  28.  Persimmon, 
Black  Walnut,  Tupelo,  Pine,  29.  Spruce,  Hemlock,  White  Cedar,  Cypress, 
30.  Larch,  Arbor  Vitae,  Red  Cedar,  Willow,  Mahogany,  31.  Boxwood, 
Lignum  Vitae,  Cork,  Hemp,  32.  Flax,  Cotton,  33.  Turpentine,  Caoutchouc, 
34.  Oils,  35.  Resins,  Starch,  Gum,  36. —  Materials  from  the  Animal  King- 
dom.— Skins,  Hair  and  Fur,  Quills,  and  Feathers,  37.  Wool,  Silk,  38.  Bone 
and  Ivory,  Horn,  Tortoise  Shell,  Whale  Bone,  39.  Glue,  Oil,  40.  Wax, 
Phosphorus,  41. 

CHAPTER  II. 

Of  the  Form,  Condition,  and  Strength  of  Materials. 

Modes  of  Estimation,  Stress  and  Strain,  42.  Resistance,  Extension,  43. 
Compression,  44.  Lateral  Strain,  Stiffness,  45.  Tubes,  Strength,  Place  of 
Strain,  46.  Incipient  Fracture,  Resilience,  47.  Shape  of  Timber,  Torsion, 
Limit  of  Bulk,  48.    Practical  Remarks,  49. 


viii 


CONTENTS. 


CHAPTER  III. 

The  Arts  of  Writing  and  Printing. 

Letters,  Invention  of  Letters,  53.  Arrangement  of  Letters,  Writing  Ma- 
terials, 54.  Papyrus,  55.  Herculaneum  Manuscripts,  56.  Parchment, 
57.  Paper,  Instruments,  Inks,  58.  Copying  Machines,  Printing,  59.  Types, 
60.  Case,  Sizes,  Composing,  Cl.  Imposing,  62.  Signatures,  Correcting 
the  Press,  63.  Press  Work,  Printing  Press,  65.  Stereotyping,  66.  Machine 
Printing,  67.    History,  68. 

CHAPTER  IV. 

Arts  of  Designing  and  Painting. 

Divisions,  Perspective,  71.  Field  of  Vision,  Distance  and  Foreshortening, 
72.  Definitions,  73.  Plate  II.,  75.  Problems,  76.  Instrumental  Perspec- 
tive, 77.  Mechanical  Perspective,  Perspectographs,  79.  Projections,  80. 
Isometrical  Perspective,  81.  Chiaro  Oscwro,  Light  and  Shade,  82.  Associa- 
tion, Direction  of  Light,  83.  Reflected  Light,  Expression  of  Shape,  84. 
Eyes  of  a  Portrait,  Shadows,  Aerial  Perspective,  85.  Coloring,  Colors,  86. 
Shades,  Tone,  Harmony,  87.    Contrast,  Remarks,  88. 

CHAPTER  V. 

Arts  of  Engraving  and  Lithography. 

Engraving,  Origin,  Materials,  90.  Instruments,  Styles,  Line  Engraving, 
91.  Stippling,  Etching,  93.  Mezzo  Tinto,  95.  Aqua  Tinta,  96.  Copper- 
plate Printing,  Colored  Engravings,  98.  Steel  Engraving,  Wood  Engraving, 
99.  Lithography,  Principles,  Origin,  100.  Lithographic  Stones,  101. 
Preparation,  Lithographic  Ink  and  Chalk,  Mode  of  Drawing,  102.  Etching 
the  Stone,  103.    Printing,  Printing  Ink,  Remarks,  104. 

CHAPTER  VI. 

Of  Sculpture,  Modelling,  and  Casting. 

Subjects,  Modelling,  106.  Casting  in  Plaster,  107.  Bronze  Casting, 
Practice  of  Sculpture,  109.  Materials,  110.  Objects  of  Sculpture,  Gem  En- 
graving, Cameos,  Intaglios,  111.    Mosaic,  Scagliola,  112. 

CHAPTER  VII. 

Of  Architecture  and  Building. 

Architecture,  Elements,  Foundations,  114.  Column,  115.  Wall,  116. 
Lintel,  Arch,  118.    Abutments,  120.    Arcade,  Vault,  Dome,  121.    Plate  L, 


CONTENTS. 


ix 


122.  Roof,  126.  Styles  of  Building,  127.  Definitions,  128.  Measures, 
Drawings,  Restorations,  130.  Egyptian  Style,  131.  The  Chinese  Style, 
The  Grecian  Style,  132.  Orders  of  Architecture,  Doric  Order,  133.  Ionic 
Order,  Corinthian  Order,  134.  Caryatides,  Grecian  Temple,  135.  Grecian 
Theatre,  137.  Remarks,  Plate  IV.,  138.  Roman  Style,  Tuscan  Order,  Ro- 
man Doric,  Roman  Ionic,  Composite  Order,  142.  Roman  Structures,  Remarks, 
143.  Plate  V.,  144.  Greco-Gothic  Style,  146.  Saracenic  Style,  Gothic 
Style,  147.  Definitions,  148.  Plate  VI.,  149.  Plate  VII,  150.  Applica- 
tion, 152. 

CHAPTER  VIII. 

Arts  of  Heating  and  Ventilation. 

Production  of  Heat,  Fuel,  Weight  of  Fuel,  153.  Combustible  Matter  of 
Fuel,  Water  in  Fuel,  154.  Charcoal,  155.  Communication  of  Heat,  Radi- 
ated and  Conducted  Heat,  Fire  in  the  Open  Air,  156.  Fire  Places,  157. 
Admission  of  Cold  Air,  Open  Fires,  Franklin  Stove,  158.  Rumford  Fire 
Place,  159.  Double  Fire  Place,  160.  Coal  Grate,  161.  Anthracite  Grate, 
Burns'  Grate,  Building  a  Fire,  162.  Furnaces,  Stoves,  163.  Russian  Stove, 
164.  Cockle,  Cellar  Stoves,  and  Air  Flues,  165.  Heating  by  Steam,  166. 
Retention  of  Heat,  Causes  of  Loss,  168.  Crevices,  Chimnies,  Entries,  and 
Sky  Lights,  169.  Windows,  Ventilation,  Objects,  Modes,  170.  Ventilators, 
Culverts,  Smoky  Rooms,  171.  Damp  Chimnies,  Large  Fire  Places,  172, 
Close  Rooms,  Contiguous  Doors,  Short  Chimnies,  Opposite  Fire  Places,  173. 
Neighbouring  Eminences,  Turncap,  &c.,  Contiguous  Flues,  174.  Burning 
of  Smoke.  175. 

CHAPTER  IX. 

Arts  of  Illumination. 

Flame,  Support  of  Flame,  176.  Torches  and  Candles,  Lamps,  177.  Re- 
servoirs, Astral  Lamp,  178.  Hydrostatic  Lamps,  179.  Automaton  Lamp. 
Mechanical  Lamps,  Fountain  Lamp,  180.  Argand  Lamp,  181.  Reflectors, 
Hanging  of  Pictures,  182,  Transparency  of  Flame,  Glass  Shades,  Sinumbral 
Lamp,  Measurement  of  Light,  183.  Gas  Lights,  184.  Coal  Gas,  185.  Oil 
Gas,  187.  Gasmeter,  Portable  Gas  Lights,  Safety  Lamp,  188.  Lamp  with- 
out Flamp,  189.    Modos  of  procuring  Light,  190. 

CHAPTER  X, 

Arts  of  Locomotion. 

Motion  of  Animal§,  192.  Inertia,  Aids  to  Locomotion,  194.  Wheel  Car- 
riages, Wheels,  195.  Rollers,  Size  of  Wheels,  196.  Line  of  Traction,  197. 
Broad  Wheels,  198.  Form  of  Wheels,  199.  Axletrees,  Springs,  Attaching 
of  Horses,  200.  Highways,  Roads,  Pavements,  202.  McAdam  Roads,  203. 
Bridges.  1.  \Vooden  Bridges,  2.  Stone  Bridge?.  20*.  3.  Cast  Iron  Rridsres, 
h 


CONTENTS. 


4.  Suspension  Bridges,  205  5.  Floating  Bridges,  Rail  Boads,  206.  Edge 
Railway,  207.  Tram  Road,  Single  Rail,  208.  Passings,  209.  Propelling 
Power,  210.  Cana/s,  Embankments,  211.  Aqueducts,  Tunnels,  212.  Gates 
and  Weirs,  Locks,  213.  Boats,  Size  of  Canals,  215.  Sailing,  Form  of  a  Ship, 
216.  Keel  and  Rudder,  217.  Effect  of  the  Wind,  218.  Stability  of  a  Ship, 
Steam  Boats,  220.  Diving  Bell,  222.  Submarine  Navigation,  224.  Aero- 
station, Balloon,  225.    Parachute,  226. 

CHAPTER  XI. 

Elements  of  Machinery. 

Machines,  Motion,  228.  Rotary  or  Circular  Motion,  Band  Wheels,  229. 
Rag  Wheels,  Toothed  Wheels,  230.  Spiral  Gear,  231.  Bevel  Gear,  232. 
Crown  Wheel,  Universal  Joint,  Perpetual  Screw,  233.  Brush  Wheels, 
Ratchet  Wheel,  Distant  Rotary  Motion,  234.  Change  of  Velocity,  235. 
Fusee,  236.  Alternate  or  Reciprocating  Motion,  Cams,  237.  Crank,  239. 
Parallel  Motion,  240.  Sun  and  Planet  Wheel,  241.  Inclined  Wheel,  Epicy- 
cloidal  Wheel,  242.  Rack  and  Segment,  Rack  and  Pinion,  243.  Belt  and 
Segment,  Scapements,  244,  Continued  Rectilinear  Motion,  Band,  245. 
Rack,  Universal  Lever,  Screw,  Change  of  Direction,  246.  Toggle  Joint, 
Of  Engaging  and  Disengaging  Machinery,  247.  Of  Equalizing  Motion, 
Governor,  248.    Fly  Wheel,  250.    Friction,  251.    Remarks,  252. 

CHAPTER  XII. 

Of  the  Moving  Forces  Used  in  the  Arts. 

Sources  of  Power,  Vehicles  of  Power,  253.  Animal  Power,  Men,  254. 
Horses,  256.  Water  Power,  Overshot  Wheel,  257.  Chain  Wheel,  260. 
Undershot  Wheel,  261.  Back  Water,  263.  Besant's  Wheel,  Lambert's 
Wheel,  284.  Breast  Wheel,  Horizontal  Wheel,  265.  Barker's  Mill,  266. 
Wind  Power,  267.  Vertical  Windmill,  Adjustment  of  Sails,  268.  Horizon- 
tal Windmill,  Steam  Power,  Steam,  270.  Applications  of  Steam,  273.  By 
Condensation,  by  Generition,  274.  By  Expansion,  275.  The  Steam  Engine, 
Boiler,  277.  Appendages,  278  Engine,  281.  Noncondensing  Engine,  282. 
Condensing  Engines,  233.  Description,  284.  Expansion  Engines,  287.  Valves, 
288.  Pistons,  289.  Parallel  Motion,  Historical  Remarks,  290.  Projected  Im- 
provements, Rotative  Engines,  292.  Use  of  Steam  at  High  Temperatures, 
293.  Use  of  Vapors  of  Low^  Temperature,  Gas  Engines,  294.  Steam  Car- 
riages, 295.  Steam  Gun,  Gunpowder,  Manufacture,  296.  Detonation, 
Force,  297.    Properties  of  a  Gun,  299.    Blasting,  300. 

CHAPTER  XIII. 

Arts  of  Conveying  Water. 

Of  Conducting  Water,  Aqueducts,  302.  Water  Pipes,  303.  Friction  of 
Pipes,  305.    Obstruction  of  Pipes,  306.    Syphon,  Of  Raising  Water,  308. 


CONTENTS. 


Scoop  Wheel,  Persian  Wheel,  309.  Noiia,  Rope  Piitnp,  Hydrcolc,  Archimi- 
des'  Screw,  310.  Spiral  Pump,  311.  Centrifugal  Pump,  Common  Pumps, 
313.  Forcing  Pump,  314.  Plunger  Pump,  315.  Dclahirc's  Pump,  Hydro- 
static Press,  316.  Lifting  Pump,  Bag  Pump,  317.  Double  Acting  Pump, 
Rolling  Pump,  318.  Eccentric  Pump,  319.  Arrangement  of  Pipes,  Chain 
Pump,  320.  Schemnitz  Vessels,  or  Hungarian  Machine,  321.  Hero's 
Fountain,  Atmospheric  Machines,  322.  Hydraulic  Ram,  323.  Of  Project- 
ing Water,  Fountains,  324.    Fire  Engines,  325.    Throwing  Wheel,  326. 

CHAPTER  XIV. 

Arts  of  Div^iding  and  Uniting  Solid  Bodies. 

Cohesion,  Modes  of  Division,  Fracture,  328.  Cutting,  Cutting  Machines, 
329.  Penetration,  Boring  and  Drilling,  330.  Turning,  331.  Attrition,  Saw- 
ing, Saw  Mill,  Circular  Saw,  332.  Crushing,  Stamping  Mill,  333.  Bark 
Mill,  Oil  Mill,  Sugar  Mill,  334.  Cider  Mill,  Grinding,  Grist  Mill,  335.  Color 
Mill,  336.  Modes  of  Union,  Insertion,  Interposition,  337.  Binding,  Lock- 
ing, Cementing,  338.  Glueing,  Welding,  339.  Soldering,  340.  Casting, 
Fluxes,  Moulds,  341. 

CHAPTER  XV. 

Arts  of  Combining  Flexible  Fibres. 

Theory  of  Twisting,  343.  Rope  Making.  344.  Cotton  Manvfacture, 
Elementary  Inventions,  346.  Batting,  347.  Carding,  Drawing,  348.  Rov- 
ing, 349.  Spinning,  Mule  Spinning,  351.  Warping,  352.  Dressing, 
Weaving,  353.  Twilling,  354.  Double  Weaving,  Cross  Weaving,  355. 
Lace,  356.  Carpeting,  Tapestry,  357.  Velvets,  Linens,  358.  Woollens, 
359.    Felting,  36\.    Paper  Making,  362. 

CHAPTER  XVI. 

Arts  of  Horology. 

Sun  Dial,  364.  Clepsydra,  365.  Water  Clock,  Clock  Work,  366.  Main- 
taining Power,  367.  Regulating  Movement,  Pendulum,  368.  Balance,  369. 
Scapement,  370.  Description  of  a  Clock,  371.  Striking  Part,  373.  De- 
scription of  a  Watch,  376. 

CHAPTER  XVII. 

Arts  of  Metallurgy. 

Extraction  of  Metals,  385.  Assaying,  Alloys,  387.  Gold,  Extraction, 
Cupellation,  389.  Parting,  Cementation,  390.  Alloy,  391.  Working,  Gold 
Beating,  392.  Gilding  on  Metals,  393.  Gold  Wire,  Silver,  Extraction,  394. 
Working,  Coining,  395.    Plating,  397.    Copper,  Extraction,  Working,  399. 


xii. 


CONTENTS. 


Brass,  Manufactures,  400.  Buttons,  Pins,  401.  Bronze,  402.  Lead,  Ex- 
traction, 403.  Manufacture,  Sheet  Lead,  Lead  Pipes,  404.  Leaden  Shot, 
405.  Tin,  Block  Tin,  Tin  Plates,  406.  Silvering  of  Mirrors,  407.  Iron, 
408.  Smelting,  409.  Crude  Iron,  Casting,  410.  Malleable  Iron,  Forging, 
412.  Rolling  and  Slitting,  413.  Wire  Drawing,  415.  Nail  Making,  Gun 
Making,  416.  Steel,  417.  Alloys  of  Steel,  Case  Hardening,  418.  Temper- 
ing, 419.    Cutlery,  421. 

CHAPTER  XVIII. 

Arts  of  Communicating  and  Modifying  Color. 

Of  Applying  Superficial  Color,  Painting,  Colors,  425.  Blues,  426.  Reds, 
427.  Yellows,  Greens,  428.  Browns,  Blacks,  429.  "Whites,  Preparation, 
Application,  Crayons,  430.  Water  Colors,  Distemper,  431.  Fresco,  En- 
caustic Painting,  Oil  Painting,  432.  Varnishing,  433.  Japanning,  435. 
Polishing,  Lacquering,  436.  Gilding,  427.  Of  Changing  Intrinsic  Color, 
Bleaching,  438.    Dyeing,  439.    Mordants,  Dyes,  440.    Calico  Printing,  444. 

CHAPTER  XIX. 

Arts  of  Vitrification. 

Glass,  Materials,  448.  Crown  Glass,  449.  Fritting,  Melting,  Blowing,  450. 
Annealing,  451.  Broad  Glass,  Flint  Glass,  Bottle  Glass,  Cylinder  Glass,  452. 
Plate  Glass,  453.  Moulding,  454.  Pressing,  455.  Cutting,  Stained  Glass,  456. 
Enamelling,  458.  Artificial  Gems,  Devitrification,  Reaumur's  Porcelain,  459. 
Crystallo-Ceramie,  Glass  Thread,  460.    Remarks,  461. 

CHAPTER  XX. 

Arts  of  Induration  by  Heat. 

Bricks,  463.  Tiles,  Terra  Cotta,  465.  Crucibles,  Pottery,  466.  Opera- 
tions, 467.  Stone  Ware,  White  Ware,  468.  Throwing,  Pressing,  Casting, 
470.  Burning,  Printing,  Glazing.  471.  China  Ware.  472.  European  Porce- 
lain, 473.    Etruscan  Vases,  474. 

CHAPTER  XXI. 

On  the  Preservation  of  Organic  Substances. 

Decomposition,  Temperature,  476.  Drynes?,  477.  Wetness,  Antiseptics, 
478.  Timber,  Felling,  479.  Seasoning,  480.  Preservation  of  Timber,  481. 
Preservation  of  Animal  Textures,  Embalming,  485.  Tanning,  486.  Parch- 
ment, Catgut,  488.  Gold  Beater's  Skin,  Speoimrns  in  Natural  History,  489. 
Appert's  Proross.  491. 


INTRODUCTION. 


Whenever  we  attempt  to  draw  a  dividing  line  between  the 
sciences,  usually  so  called,  and  the  arts,  it  results  in  distinctions, 
which  are' comparative,  rather  than  absolute.  In  many  branch- 
es of  human  knowledge,  the  two  are  so  blended  together,  that 
it  is  impossible  to  make  their  separation  complete.  In  common 
language  we  apply  the  name  of  sciences,  to  those  departments 
of  knowledge  which  are  more  speculative,  or  abstract,  in  their 
nature,  and  which  are  conversant  with  truths  or  with  phenom- 
ena, that  are  in  existence  at  the  time  we  contemplate  them. 
The  arts,  on  the  contrary,  are  considered  as  departments  of 
knowledge,  which  have  their  origin  in  human  ingenuity,  which 
depend  on  the  active,  or  formative  processes  of  the  human 
mind,  and  which  without  these,  would  not  have  existed.  Our 
knowledge  may  be  said  to  have  been  found  out  originally  by 
discovery  and  invention.  Discovery  is  the  process  of  science  ; 
invention  is  the  work  of  art.  So  common,  however,  is  the 
connexion  of  the  two  with  each  other,  that  we  find  both  a  science 
and  an  art  involved  in  the  same  branch  of  study.  For  exam- 
ple, chemistry  is  a  science  depending  on  the  immutable  rela- 
tions of  matter,  which  relations  must  have  existed,  had  there 
never  been  minds  to  study  them.  Yet  these  laws  of  matter 
would  not  have  become  the  subjects  of  science,  had  not  man- 
kind invented  the  art  of  separating  their  agents,  and  making  them 
cognizable  to  the  senses.  To  build  a  ship,  to  construct  a  watch, 
1 


2 


INTRODUCTION. 


or  to  paint  a  picture,  are  all  operations  of  art ;  yet  they  all  have 
their  foundation  in  a  certain  acquaintance  with  mathematical 
rules,  and  principles  of  natural  philosophy.  Those  artists,  who 
work  with  a  thorough  knowledge  of  principles,  we  are  accus- 
tomed to  denominate  scientific  ;  while  those  who  experiment  at 
random,  or  who  blindly  copy  the  results  of  others,  we  consider 
empirical.  Thus  it  appears  that  an  intimate  connexion  and  de- 
pendence exists  between  sciences  and  arts,  and  it  follows  that 
the  claim  which  they  offer  to  our  attention  is  in  a  great  measure 
of  the  same  kind.  Of  the  latter,  as  well  as  the  former,  we  al- 
ready require  some,  as  branches  of  a  common  education ;  while 
of  the  rest  there  are  few  which  may  not  be  advantageously 
studied,  either  as  affording  exercise  for  talents,  discipline  for 
taste,  or  practical  advantage  in  the  common  concerns  of  life. 

The  connexion  of  the  arts  with  the  sciences  is  more  common 
and  obvious  in  modern  times,  than  it  was  in  the  days  of  antiquity. 
During  the  process  of  civilization,  or  the  whole  period  which 
elapses  between  barbarism  and  complete  refinement,  the  arts 
have  uniformly  taken  precedence  both  of  science  and  literature. 
Rude  nations  commence  the  improvement  of  their  state,  by  an 
attention  to  agriculture,  to  building,  to  navigation,  and  to  sculp- 
ture. The  want  of  an  acquaintance  with  the  real  or  scientific 
principles  of  these  arts,  obliges  them  to  substitute  the  effects  of 
manual  labour  and  dexterity,  for  scientific  method  ;  and  hence 
the  paths  in  which  they  excel,  have  been  usually  of  a  different 
character  from  those  of  people  whose  knowledge  and  resourc- 
es are  greater.  The  ancients,  who  were  but  recently  descend- 
ed from  barbarians,  were  obliged  to  make  the  most  of  small 
means,  because  the  stock  of  previous  or  common  information, 
from  which  they  could  draw,  was  extremely  limited.  The 
moderns  have  the  accumulated  learning  of  ages  before  them, 
and  have  only  to  select  and  apply  their  agents  from  among  a 
multitude  of  means  already  discovered.  The  qualities,  by 
which  the  former  arrived  at  excellence,  were  more  or  less  con- 
centrated in  individuals ;  while  with  us  the  means  of  excellence 
are  recorded  in  books,  and  are  at  the  disposal  of  communities 


liNTllOJ)UCT10N. 


3 


They  possessed  the  quick  eye,  the  expert  hand,  acute  taste  and 
unwearied  industry.  For  these  we  substitute  preparatory 
science,  economical  computation,  and  mechanical  power. 
Their  processes  differed  from  ours,  as  the  process  of  the  savage 
who  fashions  and  polishes  his  war  club,  by  the  truth  of  his  eye, 
and  the  patience  and  dexterity  of  his  hand ;  differs  from  that  of 
the  civilized  mechanic,  who  turns  the  same  kind  of  thing, 
in  a  lathe,  which  another  man  has  invented  for  him,  in  a  hundredth 
part  of  the  time.  The  ancients  were  prodigal  of  means  and  lav- 
ished men  and  treasures  when  any  great  work  was  to  be  accom- 
plished. The  moderns  save  expense,  and  labour,  and  time  in  eve- 
rything. The  economy  of  the  ancients  consisted  in  diminishing 
their  personal  wants  ;  ours,  in  devising  cheap  means  to  gratify 
them.  They  prepared  their  soldiers  for  war  by  inuring  them 
to  hunger  and  fatigue  ;  we,  by  keeping  them  well  fed  and 
clothed.  Their  stateUest  edifices  were  destitute  of  cliimnies 
and  glass  windows,  yet  when  left  to  themselves,  they  have  stood 
for  thousands  of  years.  Ours  abound  in  the  means  of  making 
their  present  tenants  comfortable,  but  are  often  built  too  cheaply 
to  be  durable.  They  conveyed  water  to  their  cities  in  immense 
horizontal  channels  supported  on  arcades  of  prodigious  elevation. 
We  convey  it  over  mountains  and  under  vallies  in  hydraulic 
pipes  of  the  most  trivial  size.  Wherever  art  could  precede 
philosophy,  the  ancients  have  exhibited  the  grandest  productions 
of  genius  and  strength  ;  but,  in  the  application  of  philosophy  to 
the  arts,  the  moderns  have  achieved,  what  neither  genius  nor 
strength,  unassisted,  could  have  performed.  The  imitative  arts, 
and  those  which  required  only  boldness  and  beauty  of  design, 
or  perseverance  in  execution,  were  carried  in  antiquity  to  the 
most  signal  perfection.  Their  sculpture  has  been  the  admira- 
tion of  subsequent  ages,  and  their  architecture  has  furnished 
models  which  we  now  strive  to  imitate,  but  do  not  pretend  to 
excel.  We  might,  if  this  were  the  place,  add  their  poetry,  and 
their  oratory,  to  the  list  of  arts  which  flourished  in  perfection 
during  the  youthfulness  of  intellectual  cultivation.  But  in  mo,€t- 
ern  times  there  is  a  maturity,  a  cautiousness,  a  habit  of  ir^uc- 


4  INTRODUCTION. 

lion,  which  is  founded  on  the  advanced  state  of  philosophic 
knowledge.  Our  arts  have  been  the  arts  of  science,  built  up 
from  an  acquaintance  with  principles,  and  with  the  relations  of 
cause  and  effect.  With  less  bodily  strength,  and  probably  with 
not  more  vigorous  intellects,  we  have  acquired  a  dominion  over 
the  physical  and  moral  world,  which  nothing  but  the  aid  of  phi- 
losophy could  have  enabled  us  to  establish.  We  convert  natu- 
al  agents  into  ministers  of  our  pleasure  and  power,  and  supply 
our  deficiencies  of  personal  force  by  the  application  of  acquired 
knowledge.  Among  us,  to  be  secure,  it  is  not  necessary  that 
a  man  should  be  powerful  and  alert ;  for  even  where  laws  fail, 
the  weak  take  rank  with  the  strong,  because  the  weakest  man 
may  arm  himself  with  the  most  formidable  means  of  defence. 
The  labor  of  a  hundred  artificers  is  now  performed  by  the  op- 
erations of  a  single  machine.  We  traverse  the  ocean  in  secur- 
ity, because  the  arts  have  furnished  us  a  more  unfailing  guide 
than  the  stars.  We  accomplish  what  the  ancients  only  dreamt 
of  in  their  fables ;  we  ascend  above  the  clouds,  and  penetrate 
into  the  abysses  of  the  ocean. 

The  application  of  philosophy  to  the  arts  is  a  more  fruitful 
theme,  than  can  w^ell  be  condensed  into  a  limited  work,  or 
course  of  instruction.  While  it  comprises  some  of  the  sources 
even  of  ancient  refinement,  it  includes  a  great  part  of  the 
grounds  of  modern  superiority.  The  application  of  philosophy 
to  the  arts  may  be  said  to  have  made  the  world  what  it  is  at 
the  present  day.  It  has  not  only  affected  the  physical,  but  has 
changed  the  moral  and  political  condition  of  society.  The  in- 
vention of  the  printing  press,  dispersed  the  darkness  of  the  mid- 
dle ages,  and  carried  truth  and  knowledge  to  every  portion  of 
the  world.  The  artificial  combination  of  sulphur,  nitre,  and 
charcoal,  has  revolutionized  the  customs  and  the  arts  of  war, 
and  even  in  military  life,  has  given  the  mind  the  advantage  over 
the  body.  The  moderns  have  imparted  magnetism  to  a  piece 
of  steel  and  suspended  it  on  a  pivot,  and  what  has  been  the 
consequence  ?  It  has  opened  to  them  a  path  across  unknown 
seas,  and  has  disclosed  a  new  continent  to  the  inhabitants  of  the 


INTRODUCTION. 


5 


old,  a  successor  to  their  arts  and  their  power.  It  has  develop- 
ed the  wealth  of  unkno^vn  islands,  has  brought  the  remotest 
countries  together,  and  has  made  the  ocean  the  resort  and  sup- 
port of  multitudes.  Let  any  one,  who  would  know  what  modern 
arts  have  accomplished,  compare  the  repeating  watch,  and  the 
unerring  chronometer  of  the  present  day,  with  the  rude  sun 
dial  and  clepsydra  of  the  ancients.  Let  him  consider  the  mul- 
tiplied advantages  which  attend  the  invention  of  glass,  which 
has  enabled  us  to  combine  light  with  warmth  in  our  houses ; 
which  has  given  sight  to  the  aged,  which  has  opened  the  heav- 
ens to  the  astronomer,  and  the  wonders  of  microscopic  life  to 
the  naturalist.  Let  him  attend  to  the  complicated  engines  and 
machinery,  which  are  now  introduced  into  almost  every  manu- 
facturing process,  and  which  render  the  physical  laws  of  inert 
matter,  a  substitute  for  human  strength. 

But  it  is  not  the  contrast  with  antiquity  alone,  that  enables  us 
to  appreciate  the  benefits  which  modern  arts  confer.  In  the 
present  inventive  age,  even  short  periods  of  time  bring  with 
them  momentous  changes.  Every  generation  takes  up  the 
march  of  improvement,  where  its  predecessors  had  stopped, 
and  every  generation  leaves  to  its  successors  an  increased  cir- 
cle of  advantages  and  acquisitions.  Within  the  memory  of 
many  who  are  now  upon  the  stage,  new  arts  have  sprung  up, 
and  practical  inventions,  with  dependant  sciences  ;  bringing  with 
them  consequences  which  have  diverted  the  industry,  and 
changed  the  aspect  of  civilized  countries.  The  augmented 
means  of  public  comfort  and  of  individual  luxury,  the  expense 
abridged  and  the  labor  superseded,  have  been  such,  that  we 
could  not  return  to  the  state  of  knowledge  which  existed  even 
fifty  or  sixty  years  ago,  without  suffering  both  intellectual  and 
physical  degradation.  At  that  time,  philosophy  was  far  distant 
from  its  present  mature  state,  and  the  arts  which  minister  to 
national  wealth  were  in  comparative  infancy.  No  man  then 
knew  the  composition  of  -the  atmosphere,  or  of  the  ocean. 
The  beautiful  and  intricate  machinery,  which  weaves  the  fabric 
of  our  clothing,  was  not  even  in  existence.    When  George  UI. 


6 


INTRODUCTION. 


visited  the  works  of  Messrs  Boulton  and  Watt  at  Birmingham, 
and  was  told  that  they  were  manufacturing  an  article  of  which 
kings  were  fond,  and  that  that  article  was  power ;  he  was  struck 
with  the  force  and  disadvantageousness  of  the  comparison. 
Yet  the  steam  engine  had  not  then  been  launched  upon  the 
ocean,  and  had  developed  only  half  its  energies. 

So  long  as  the  arts  continue  to  exert  the  influence,  and  to 
yield  the  rewards,  which  they  have  hitherto  done,  there  will  be 
no  want  of  competent  minds  and  hands,  to  carry  forward  their 
advancement.  With  their  increasing  consequence,  there  must 
also  be  an  increasing  attention  to  their  study  and  dissemination. 
Curiosity  keeps  pace  with  the  interest  and  magnitude  of  its 
objects.  And  unless  the  character  of  the  present  age  is  greatly 
mistaken,  the  time  may  be  anticipated  as  near,  when  a  know- 
ledge of  the  elements  and  language  of  the  arts  will  be  as  essen- 
tially requisite  to  a  good  education,  as  the  existence  of  the  same 
arts  is  to  the  present  elevated  condition  of  society. 


ELEMENTS  OF  TECHNOLOGY. 


CHAPTER  1. 

OF  MATERIALS  USED  IN  THE  ARTS. 

The  mineral,  vegetable,  and  animal  kingdoms,  respectively 
contribute  to  supply  the  substances  which  are  necessary  in  the 
arts.  Of  these  substances,  many  have  been  known  and  used 
from  the  time  of  the  earliest  records  ;  others  are  of  recent  in- 
troduction, and  additions  are  still  making  to  the  stock  previously 
known.  The  value  of  a  substance  to  the  arts,  may  be  estima- 
ted from  the  importance  of  the  object  it  fulfils,  its  durability, 
the  number  of  purposes  to  which  it  may  be  applied,  and  the 
facility  with  which  it  is  convertible  to  use. 

MATERIALS  FROM  THE  MINERAL  KINGDOM. 

Stones  and  Earths. — Marble. — The  class  of  stones  denom- 
inated calcareous,  is  exceedingly  numerous  and  abundant  in  na- 
ture. Of  these  marble  is  the  most  important.  It  is  a  granular 
carbonate  of  lime,  varying  in  color,  texture,  and  hardness.  Mar- 
ble is  extensively  used  for  building,  statuary,  decorations,  and  in- 
scriptions. In  warm  countries  it  is  one  of  the  most  durable  of 
substances,  as  is  proved  by  the  edifices  of  Athens,  which  have  re- 
tained their  polish  for  more  than  two  thousand  years.  Severe 
frost,  preceded  by  moisture,  causes  it  to  crack  and  scale.  Great 


8 


MATERIALS  USED   IN  THE  ARTS. 


heat  reduces  it  to  quicklime.  Marble  is  wi'ought  by  chiseling, 
and  by  sawing  with  smooth  plates  of  iron,  with  sand  and  water. 
It  is  polished  by  rubbing  with  sand  and  water,  and  afterwards 
with  putty  and  soft  substances. 

Numerous  stones  of  the  calcareous  class,  more  or  less  ap- 
proaching to  marble  in  their  character,  have  been  converted  to 
use  in  different  countries.  The  Pyramids  of  Egypt  are  built 
of  a  greyish  white  calcareous  stone,  inclosing  shells.  ^  The 
Parthenon,  and  other  structures  of  Atliens,  are  of  Pentelic  mar- 
ble, distinguished  by  slight  greenish  veins.  The  mosques  of 
Constantinople  are  of  a  fine  grained  limestone  from  Pappenheim, 
the  same  wliich  is  now  used  in  lithography.  At  Rome,  a  po- 
rous whitish  limestone,  called  tophus  by  the  ancients,  and  trav- 
ertino  by  the  moderns,  is  the  material  of  the  Coliseum,  of  St 
Peter's  church,  &;c.  The  ruins  of  Paestum  are  of  a  stone 
nearly  similar.  The  building  called  the  Tomb  of  Theodoric, 
at  Ravenna,  has  a  dome  consisting  of  a  single  stone  which  is 
thirtyfour  feet  in  diameter.  It  is  a  grey  limestone  from  Istria, 
and  is  computed  to  have  weighed,  when  taken  from  the  quarry, 
more  than  two  million  pounds,  f  Paris  is  built  with  calcareous 
stone,  of  which  there  are  five  kinds.  The  Portland  stone  of 
which  St  Paul's  and  other  edifices  in  London  are  constructed, 
is  a  calcareous  rock  called  Oolite  by  mineralogists.  Specimens 
of  marble  abound  in  the  United  States,  and  are  seen  in  the 
City  Hall  of  New  York,  the  United  States  and  Pennsylvania  » 
Banks,  Philadelphia,  the  Washington  Monument,  Baltimore,  &,c. 

In  statuary  the  Venus  de  Medicis,  and  Diana  venatrix,  are 
formed  of  Parian  marble.  The  Apollo  de  Belvidere,  accord- 
ing to  Dolomieu,  is  made  of  Luni  marble,  and  if  so  must 
be  posterior  to  the  time  of  Julius  Cassar,  before  which  period 
that  quarry  was  not  opened. 

Granite. — Granite  is  apparently  the  oldest  and  the  deepest 
of  rocks.  It  is  one  of  the  hardest  and  most  durable  which  have 
been  wrought,  and  is  obtained  in  larger  pieces  than  any  other 


*  Brard. 


t  Borgnis. 


MATERIALS   USED   IN  THE  ARTS. 


9 


rock.  Granite  is  a  compound  stone,  varying  in  color  and 
coarseness.  It  consists  of  thi'ee  constituent  parts  ;  viz.  quartz^ 
the  material  of  rock  crystal ;  feldspar^  which  gives  its  colors, 
and  which  is  the  material  of  porcelain  earth  ;  and  lastly  mica, 
a  transparent,  thin,  or  foliated  substance,  which  affords  a  flexible 
substitute  for  glass,  when  obtained  in  large  pieces.  Granite  is 
chiefly  used  for  building.  It  is  split  from  the  quarries  by  rows 
of  iron  wedges  driven  simultaneously  in  the  direction  of  the  in- 
tended fissure.  This  method  is  thought  by  Brard  to  hav  e  been 
known  to  the  ancient  Romans  and  Egyptians.  The  blocks  are 
afterwards  hewn  to  a  plane  surface  by  strokes  of  a  shnrp  edged 
hammer.  Granite  is  also  chiselled  into  capitals  and  decorative 
objects,  but  this  operation  is  diflicult,  owing  to  its  hardness  and 
brittleness.  It  is  polished  by  long  continued  friction,  with  sand 
and  emery. 

The  largest  mass  of  granite,  known  to  have  been  transported 
in  modern  times,  is  the  pedestal  of  the  equestrian  statue  of  Pe- 
ter the  Great,  at  St  Petersburgh.  It  is  computed  to  weigh  three 
million  pounds,  and  was  transported  nine  leagues  by  rolling  it 
on  cannon  balls.  ^  Those  of  cast  iron  being  crushed,  others  of 
bronze  were  substituted.  Sixty  granite  columns  at  St  Peters- 
burgh, consist  each  of  a  single  stone  twenty  feet  high.  The 
columns  in  the  portico  of  the  Pantheon  at  Rome,  which  are 
thirtysix  feet,  eight  inches  high,  are  also  of  granite,  f  The 
shaft  of  Pompey's  Pillar,  so  called,  J  in  Egypt,  is  sixtythree  feet 
in  height,  and  of  a  single  piece.  It  is  said  to  be  of  red  gran- 
ite, but  is  possibly  sienite.  In  the  Eastern  part  of  the  United 
States,  a  beautiful  white  granite  is  found  in  various  places,  and 
is  now  introduced  in  building.  The  new  IMarket  Ilouse  in 
Boston,  the  United  States  Bank,  &ic.  are  made  of  it. 

Sienite. — This  rock  is  related  to  granite,  and  resembles  it  in 
its  general  characters.  It  consists  chiefly  of  feldspar  and  horn- 
blende.   Sienite  is  obtained  in  large  pieces,  and  possesses  all 

*  Carburi.  t  Rondelet. 

t  The  inscription  on  this  pillar  is  said  by  the  Earl  of  Mountnorris  in  Brande's 
Journal,  to  belong  to  Dioclesian,  and  not  to  Ponipey,as  was  formerly  supposed. 
.2 


10 


MATERIALS  USED   IN  THE  ARTS. 


the  valuable  properties  of  granite  ;  but  being  harder,  it  is  some- 
what more  difficult  to  chisel.  It  is  found  in  Egypt,  and  con- 
stitutes the  material  of  many  of  the  obelisks.  The  Romans 
hnported  it  from  that  country.  Sienite  is  found  abundantly 
near  Boston,  and  is  introduced  into  many  structures.  The 
Washington  Bank,  and  the  Bunker  Hill  Monument  consist  en- 
tirely of  this  stone.  Its  extreme  hardness  renders  it  one  of  the 
best  materials  for  M'Adam  roads.  A  railway  is  built  at  Quin- 
cy  for  transporting  the  stone  from  the  quarry  to  the  sea,  and  the 
name  of  Quincy  Stone  is  now  commonly  applied  to  it. 

Freestone. — Freestone  consists  of  sand,  or  siliceous  particles, 
united  by  a  cement.  It  is  also  called  sandstone.  It  varies  in 
color  from  greyish  white,  to  red  and  dark  brown.  It  is  of  mod- 
erate hardness,  in  general,  and  easily  wrought  by  the  chisel. 
Varieties  of  freestone  are  used  in  building  in  different  parts  of 
Europe.  In  Africa  the  temple  of  Hermopolis  is  composed  of 
enormous  masses  of  this  stone.  In  America,  the  Capitol  at 
Washington  is  of  the  Potomac  freestone,  likewise  the  fagade  of 
St  Paul's  Church  in  Boston.  This  stone  is  jised  for  various 
other  practical  purposes,  particularly  the  grinding  of  steel 
instruments,  and  the  filtering  of  water. 

Slate. — Slates  are  valuable  for  the  property  of  splitting  in 
one  direction,  so  as  to  afford  large  fragments  which  are  perfectly 
flat,  and  thin.  The  best  slates  are  those  which  are  even,  com- 
pact, and  sonorous  ;  and  which  absorb  the  least  water  on  being 
immersed.  Slates  are  much  used  as  an  incombustible  covering 
for  the  roofs  of  houses.  Tablets,  gravestones,  and  writing 
slates,  are  also  formed  from  them.  ^ 

Soapstone. — This  stone  is  usually  of  a  greyish  color,  mode- 
rately soft,  and  having  an  unctuous  feel,  which  is  compared  to 
that  of  soap.  It  is  remarkable  for  bearing  heat,  and  sudden 
changes  of  temperature,  without  injury.    It  receives  a  tolerable 

*  Various  artificial  compositions  have  been  employed  as  substitutes  for  slate, 
in  forming  waterproof  coverings  for  roofs.  One  of  these,  which  appears  to 
have  been  successfully  used  in  the  north  of  Europe  is  formed  of  bolar  earth, 
chalk,  glue,  pulp  of  paper,  and  linseed  oil.    Franklin  Journal,  iv.  89. 


MATERIALS   USED   IN   THE  ARTS. 


11 


polish.  Soapstone,  on  account  of  its  softness,  is  wrought  with 
the  same  tools  as  wood.  It  is  sometimes  used  in  building,  but 
is  not  always  durable.  It  is,  however,  of  great  importance  in 
the  construction  of  fireplaces  and  stoves,  and  is  extensively  used 
for  this  purpose.  Slabs  of  good  soapstone,  when  not  exposed 
to  mechanical  injury,  frequently  last  eight  or  ten  years,  under 
the  influence  of  a  common  fire  on  one  side,  and  of  cold  air  on 
the  other.  It  grows  harder  in  the  fire,  but  does  not  readily 
crack,  nor  change  its  dimensions  sufficiently  to  affect  its  useful- 
ness. Owing  to  the  facility  with  which  it  is  wrought,  its  joints 
may  be  made  sufficiently  tight  without  dependance  on  cement. 
Among  the  best  quarries  for  fireproof  stone,  is  that  of  Fran- 
cestown.  New  Hampshire.  Soapstone  is  manufactured  into 
various  vessels  and'utensils,  and  is  advantageously  employed  for 
aqueducts.  It  is  lately  found  to  be  one  of  the  best  materials 
for  counteracting  friction  in  machinery,  for  which  purpose  it  is 
<-    used  in  powder  mixed  with  oil. 

Serpentine. — Serpentine  is  a  smooth,  compact  stone,  more 
or  less  of  a  greenish  color,  composed  chiefly  of  magnesia  and 
silex.  It  is  sufficiently  soft  to  be  scratched  with  a  knife,  and 
receives  a  pohsh  like  that  of  marble.  It  is  used  in  building,  in 
Florence  and  other  parts  of  Italy,  and,  in  Saxony,  is  wrought 
into  many  small  articles  of  ornament. 

Gypsum. — Gypsum,  called  in  commerce  Plaster  of  Paris,  is  a 
sulphate  of  lime,  of  which  there  are  many  varieties.  When 
dried  by  heat,  ground  to  fine  powder,  and  mixed  with  water,  it 
has  the  property  of  becoming  hard  in  a  few  minutes,  and  of 
receiving  accurately  the  impression  of  the  most  delicate  moulds. 
It  is  extensively  employed  for  stucco  working,  and  plastering 
of  rooms.  It  furnishes  a  delicate,  white,  and  smooth  material 
for  casts  of  statues,  architectural  models,  impressions  of  seals, 
&c.  In  the  art  of  stereotyping  it  is  indispensable.  It  is  used 
in  agriculture  to  fertilize  certain  soils. 

Alabaster. — ^Under  this  name  two  substances  are  known  in 
commerce.  One  is  a  carbonate  of  lime  deposited  by  the  drip- 
ping of  water  in  stalactitic  caves.    The  other,  and  the  most 


12 


MATERIALS   USED   IN   THE  ARTS. 


common,  is  a  compact  gypsum.  This  is  softer  than  marble, 
translucent,  and  susceptible  of  a  fine  polish.  Many  beautiful 
ornaments,  such  as  vases,  statues,  shades  for  lights,  he,  are 
made  from  it.  As  alabaster  of  the  last  species  is  soluble  in 
five  hundred  parts  of  water,  Mr  Moore  has  proposed  an  easy 
method  of  cleansing  it,  by  immersing  it  for  about  ten  minutes 
in  water,  and  afterwards  rubbing  it  with  a  brush  dipped  in  dry, 
powdered  plaster. 

Chalk. — Chalk  is  a  soft  carbonate  of  lime,  the  properties  of 
which  are  well  known.  It  is  used  as  the  basis  of  various  white 
pigments,  and  cementing  substances.  Common  whiting  is  pu- 
rified chalk,  prepared  by  reducing  the  chalk  to  fine  powder  and 
agitating  it  with  water.  The  sand  and  coarser  particles  first  sub- 
side, after  which  the  water  is  drawn  off  and  the  whiting  suffered 
to  deposit  itself.    Chalk  by  calcination  furnishes  excellent  lime. 

Fluor  Spar. — This  is  a  fluate  of  lime.  The  variety  chiefly 
used  is  the  Derbyshire  spar,  which  is  beautifully  variegated  with 
purple  and  other  colors.  Ornamental  objects  and  utensils  are 
made  from  it.  Its  acid,  when  disengaged,  is  sometimes  used 
to  corrode  glass. 

Flint. — Flint  is  found  in  roundish  masses  and  is  composed 
almost  wholly  of  silex.  Its  extreme  hardness  causes  it  to  strike 
fire  readily  with  steel,  from  which  property  its  greatest  use  is 
derived.  Gun-flints  are  formed  by  practised  workmen,  who 
break  them  out  with  a  hammer,  a  roller,  and  steel  chisel,  with 
small  repeated  blows.  Flints  are  used  also  in  the  manufactures 
of  glass,  porcelain,  and  Wedgev.^ood's  ware.  For  this  purpose 
they  are  reduced  to  fine  powder  by  heating  red  hot  and  plung- 
ing them  in  water  ;  afterwards  by  pounding,  sifting,  and  wash- 
ing.   Flints  are  broken  up  to  form  M'Adam  roads. 

Porphyry. — Porphyry  is  a  variegated  stone  consisting  of 
small  crystals  of  feldspar  or  quartz  imbedded  in  a  basis  of  a 
darker  color.  It  receives  a  beautiful  polish,  but  its  extreme 
hardness  renders  it  diflicult  to  work.  The  ancients  made  col- 
umns and  even  statues  of  this  material,  but  the  moderns  con- 
fine its  use  chiefly  to  smaller  works,  such  as  vases,  boxes,  mor- 
tars, &:c. 


MATERIALS  USED   IN  THE  ARTS. 


13 


Buhrstonc, — This  is  a  hard,  siliceous  stone,  remarkable  for 
its  cellular  structure ;  containing  always  a  greater  or  less  num- 
ber of  irregular  cavities.  Hence  its  surface,  however  worn  and 
levelled,  is  always  rough.  This  property  renders  buhrstone 
an  invaluable  material  for  millstones.  When  it  is  not  found  of 
sufficient  size  for  this  use,  small  pieces  of  it  are  fitted  together, 
cemented,  and  bound  with  an  iron  hoop.  It  is  imported  from 
France,  and  is  also  found  in  some  localities  in  the  United  States. 

JVovacuUte. — This  stone  is  commonly  known  under  the  names 
of  hone,  Turkey  oilstone,  &£c.  It  is  of  a  slaty  structure  and 
owes  its  power  of  whetting,  or  sharpening  steel  instruments,  to 
the  fine  siliceous  particles  which  it  contains.  Various  other 
stones  are  used  as  whetstones,  such  as  common  slate,  mica  slate, 
freestone,  &ic. 

Precious  Stones. — These  are  better  known  as  objects  of  lux- 
ury, than  of  use  ;  yet  their  preparation  gives  rise  to  an  exten- 
sive branch  of  industry.  They  are  in  general  distinguished  for 
their  small  size,  and  great  brilliancy,  permanency,  and  hardness. 
The  latter  quality  renders  them  useful  in  the  arts.  The  dia- 
mond is  generally  employed  for  cutting  sheets  of  glass.  The 
diamond,  ruby,  sapphire,  and  some  others,  are  used  by  watch- 
makers for  pivot  holes  to  diminish  the  friction  of  their  verges 
and  axles.  These  stones  are  wrought  by  grinding  them  with 
emery  and  other  hard  powders.  The  diamond  can  only  be  cut 
with  its  own  dust.  Various  hard,  siliceous  stones  of  less  value, 
as  the  carnelian,  jasper,  agate,  he,  are  used  by  lapidaries,  for 
engraving  seals,  cameos,  and  other  objects  of  ornament. 

Emery. — The  best  emery  is  a  variety  of  the  corundum  stone, 
obtained  chiefly  from  the  island  of  Naxos,  in  the  Ai^chipelago . 
Several  other  substances,  however,  are  sold  under  this  name. 
Emery  is  the  hardest  of  all  known  substances,  except  the  dia- 
mond, and  its  powder  is  extensively  used  in  grinding  and  pol 
ishing  metals,  stones,  and  glass.  It  is  reduced  to  powder  by 
grinding  it  in  a  steel  mill,  and  is  afterwards  assorted  into  parcels 
of  different  fineness,  by  agitating  it  with  water,  and  separating 
the  particles  which  deposit  themselves  at  different  times ;  tlie 
finest  particles  being  the  last  which  subside. 


14 


MATERIALS  USED   IN  THE  ARTS. 


Sand. — Sand  of  the  best  quality,  is  that  which  consists  of 
particles  of  pure  quartz,  and  such  only  is  used  in  the  manufac- 
ture of  fine  glass.  It  is  found  in  various  localities,  but  is  most 
commonly  procured,  in  this  country,  from  the  banks  of  the  Del- 
aware. Impure  sand  answers  only  for  bottles  and  inferior  glass. 
For  mechanical  purposes,  such  as  grinding  glass  and  marble, 
sharp  sand,  the  particles  of  which  are  angular,  is  best.  The 
sand  used  for  moulds  by  brass  founders,  possesses  a  somewhat 
argillaceous  character,  sufficient  to  render  it  moderately  cohe- 
sive when  wet,  in  consequence  of  which  quality  it  retains  its 
shape.  The  sand  used  in  mortar,  should  be  sharp,  and  free 
from  all  perishable  or  dehquescent  ingredients. 

Pumice. — This  is  a  spongy,  porous  stone,  of  a  fibrous  tex- 
ture, and  so  light  as  often  to  swim  in  water.  It  is  considered 
to  be  of  volcanic  origin.  It  is  employed  to  grind  the  surface 
of  metals,  and  other  minerals.  On  account  of  its  lightness,  it 
is  sometimes  used  to  construct  domes,  vaults,  and  other  elevat- 
ed parts  of  buildings.  The  dome  of  the  mosque  of  St  Sophia, 
at  Constantinople,  is  said  to  be  of  this  material. 

Tripoli. — This  mineral  resembles  certain  clays,  but  is  rough 
and  friable,  and  does  not  form  a  paste  with  water.  It  posses- 
ses a  fine  hard  grit,  and  is  used  to  polish  metals  and  stones. 
Common  rotten  stone,  and  polishing  slate,  are  varieties  of 
tripoli. 

Clay. — This  abundant  and  useful  earth,  is  composed  princi- 
pally of  alumine  and  silex.  It  possesses  the  valuable  property 
of  forming,  when  wet,  a  ductile  and  tenacious  paste,  which  is 
changed  by  heat  to  a  stony  hardness.  Common  clay,  of  which 
bricks  and  coarse  potter's  ware  are  made,  contains  oxide  of  iron, 
which  causes  it  to  turn  red  in  burning.  The  purer  sorts,  such 
as  pipe  clay,  become  whiter  when  exposed  to  a  high  heat. 
The  earthy  smell,  which  clays  emit  when  breathed  upon,  ap- 
pears also  to  be  owing  to  oxide  of  iron.  Absolutely  pure  clays 
emit  no  smell.  Refractory  clays  are  those  which  endure  the 
greatest  heat  without  melting.  The  best  fireproof  bricks  and 
crucibles  are  made  from  slate  clay,  and  contain  a  good  deal  of 


MATERIALS  USED   IN  THE  ARTS. 


15 


sand.  Sometimes  they  are  made  of  old  materials,  which  have 
been  before  exposed  to  high  heat,  pounded  up  and  mixed  with 
fresh  clay.  A  mixture  of  two  parts  of  Stourbridge  clay  and 
one  part  of  coke,  has  been  found  very  refractory. 

Asbestus. — Asbestus  is  a  mineral  of  a  fibrous  structure.  One 
of  its  varieties,  called  Amianthus,  is  composed  of  very  delicate, 
flexible  filaments,  resembling  fibres  of  silk.  It  has  been  man- 
ufactured into  cloth  and  paper,  which  possess  the  property  of 
being  incombustible.  It  is  difficult,  however,  to  find  fibres  of 
sufficient  length  and  firmness,  to  produce  objects  of  any  great 
use.  It  is  sometimes  mixed  with  clay  in  pottery,  to  increase  its 
strength.  It  has  also  been  used  for  the  packing  of  steam  en- 
gines which  are  of  high  pressure,  or  in  which  steam  is  used  at 
an  elevated  temperature. 

Cements. — Limestone. — The  substances  made  use  of  for 
the  uniting  medium  between  bricks  or  stones  in  building,  are 
denominated  cements.  The  calcareous  cements,  composed 
of  a  mixture  of  lime,  sand,  and  water ;  in  consequence  of  the 
facility  with  which  they  pass  from  a  soft  state  to  a  stony  hard- 
ness, have  in  common  uses  uperseded  all  others.  Lime  in 
the  state  of  quicklime,  is  obtained  by  burning  in  kilns,  any  of 
those  natural  bodies,  in  which  it  exists  in  combination  vdth  car- 
bonic acid ;  such  as  limestone,  marbles,  chalk,  and  shells.  The 
effect  of  the  burning,  or  calcination,  is  to  drive  off  the  carbonic 
acid.  If  quicklime,  thus  obtained,  be  wet  with  water,  it  instantly 
swells  and  cracks,  becomes  exceedingly  hot,  and  at  length  falls 
into  a  white,  soft,  impalpable  powder.  This  process  is  denomi- 
nated the  slaking  of  the  lime.  The  compound  formed  is  called 
a  hydrate  of  lime,  and  consists  of  about  three  parts  of  lime  to 
one  of  water.  When  intended  for  mortar  it  should  immediately 
be  incorporated  with  sand,  and  used  without  delay,  before  it 
imbibes  carbonic  acid  anew  from  the  atmosphere.  Lime,  thus 
mixed  with  sand,  becomes  harder  and  more  cohesive  and  dura- 
ble, than  if  it  were  used  alone.  It  is  found  that  the  sand  used 
in  common  mortar,  undergoes  little  or  no  change ;  while  the  lime, 
Seemingly  by  crystalization,  adheres  to  its  particles,  and  unites 


J6  MATERIALS  USED   IN  THE  ARTS. 

them  together.  *  Cements  composed  in  this  manner  continue 
to  increase  in  strength  and  soHdity  for  an  indefinite  period,  the  hy- 
drate of  lime  being  gradually  converted  into  a  corbonate.  The 
sand  most  proper  to  form  mortar,  is  that  which  is  wholly  sili- 
ceous, and  which  is  sharp,  that  is,  not  having  its  particles  round- 
ed by  attrition.  Fresh  sand  is  to  be  preferred  to  that  taken 
from  the  Vicinity  of  the  seashore,  the  salt  of  which  is  liable  to 
deliquesce  and  weaken  the  strength  of  the  mortar.  The  pro- 
portions of  the  lime  and  sand  to  each  other,  are  varied  in  differ- 
ent places  ;  tlie  amount  of  sand,  however,  always  exceeds  that 
of  the  Hme.  The  more  sand  can  be  incorporated  with  the 
hme,  the  better,  provided  the  necessary  degree  of  plasticity  is 
preserved ;  for  the  cement  becomes  stronger,  and  it  also  sets,  or 
consolidates  more  quickly,  when  the  hme  and  water  are  less  in 
quantity  and  more  subdivided.  From  two  to  four  parts  of  sand 
are  used  to  one  of  lime,  according  to  the  quality  of  the  lime 
and  the  labour  bestowed  on  it.  The  more  pure  is  the .  lime 
and  the  more  thoroughly  it  is  beaten  or  worked  over,  the 
more  sand  it  will  take  up,  and  the  more  firm  and  durable  does 
it  become. 

PuzzoJana. — Water  cements,  or  hydraulic  cements,  often 
called,  also,  Roman  cements,  are  those  which  have  the  property 
of  hardening  under  water,  and  of  consoHdating  almost  immedi- 
ately on  being  mixed.  Common  mortar,  although  it  stands  the 
effect  of  water  very  well  when  perfectly  dry,  yet  occupies  a 
considerable  time  in  becoming  so,  and  dissolves  or  crumbles 
away,  if  laid  under  water  before  it  has  had  time  to  harden.  It 
is  found  that  certain  rocks  which  possess  an  argillaceous  as  well 
as  sihceous  character,  if  mixed  with  lime  or  mortar,  communi- 
cate to  them  the  property  of  hardening  in  a  very  few  minutes 
after  the  mixture  has  taken  place,  as  well  under  water  as  out 
of  it.  Substances  of  this  sort  have  therefore  been  made  the 
basis  of  water  cements.  The  ancient  Romans,  who  practised 
building  in  the  water,  and  particularly  in  the  sea,  to  a  great  ex- 


*  See  Brard  and  Vicat  on  this  subject. 


MATERIALS  USED  IN   THE  ARTS. 


tent,  first  availed  themselves  of  a  material  of  this  kind.  The 
Bay  of  Baiae,  from  the  coolness  and  salubrity  of  its  situation,  was 
a  place  of  fashionable  resort  for  the  wealthy  of  Rome,  during 
the  summer  months.  They  erected  their  villas,  not  only  on  the 
seashore,  but  on  artificial  quays  and  islands  constructed  in  the  wa- 
ter. To  enable  them  to  erect  these  marine  structures,  they 
fortunately  discovered,  at  the  town  of  Puteoli,  a  peculiar  earth, 
to  which  they  gave  the  name  of  pulvis  puteolanus,  and  which 
is  the  same  now  known  by  the  name  of  Puzzolana.  This  earth 
is  a  light,  porous,  friable  mineral,  various  in  color,  and  evidently 
of  volcanic  origin.  When  reduced  to  uniform  powder  by  beat- 
ing and  sifting,  and  thoroughly  mixed  with  lime,  either  with  or 
without  sand,  it  forms  a  mass  of  great  tenacity,  which  in  a  short 
time  concretes  to  a  stony  hardness,  not  only  in  the  air,  but 
likewise  when  wholly  immersed  in  water. 

Tarras. — A  substance  denominated  tarras,  terras,  or  trass, 
found  near  Andernach  in  the  vicinity  of  the  Rhine,  has  been 
discovered  to  possess  the  same  property  with  puzzolana,  of  form- 
ing a  durable  water  cement,  when  combined  with  lime.  It  is 
said  to  be  a  kind  of  decomposed  basalt,  but  resembles  puzzo- 
lana. It  is  the  material  which  has  been  principally  employed 
by  the  Dutch,  whose  aquatic  structures  probably  exceed  those 
of  any  other  nation  in  Europe.  Tarras  mortar,  though  very 
durable  in  water,  is  inferior  to  the  more  common  kinds,  when 
exposed  to  the  open  air. 

Other  Cements. — It  has  been  found  that  various  other  sub- 
stances, such  as  baked  clay  reduced  to  powder,  or  the  common 
greenstone  calcined  and  pulverized,  afford  the  basis  of  very 
tolerable  water  cements,  with  lime.  Some  of  the  ores  of  man- 
ganese are  also  useful  for  the  same  purpose. 

There  are  some  limestones  which  have  the  property  of  form- 
ing water  cements  when  calcined  and  mixed  with  simple  sand 
and  water.  This  is  usually  in  consequence  of  these  stones 
containing  a  certain  portion  of  argillaceous  earth,  united  with 
the  lime.  A  water  cement  found  in  New  York,  was  used  in 
constructing  the  locks  of  the  great  canal  in  that  State.  Another 
3 


18 


MATERIALS  USED  IN  THE  ARTS. 


hydraulic  cement,  containing  lime,  silex,  and  alumine,  has  been 
found  and  applied  to  use  in  the  Union  Canal  of  Pennsylvania.  * 

The  cause  by  which  these  compounds  become  hard  under 
water,  is  not  satisfactorily  known.  It  has  been  supposed,  how- 
ever, and  not  without  reason,  that  the  great  attraction  for  mois- 
ture existing  in  certain  argillaceous  earths,  causes  them  to  ab- 
sorb immediately  the  superabundant  moisture  from  the  lime,  and 
thus  to  expedite  its  solidification.  This  explanation  is  render- 
ed more  probable,  by  the  fact,  that  burnt  clays,  which  form 
good  hydraulic  cements ;  cease  to  do  so,  if  the  burning  is  car- 
ried so  far  as  to  vitrify  them,  f 

Maltha. — The  name  of  maltha,  or  mastich,  is  given  to 
those  cements  into  which  animal  and  vegetable  substances  enter, 
such  as  oil,  milk,  mucilage,  he.    Some  of  these  mixtures  have 

*  M.  Berthier  states  that  with  one  part  of  common  clay  and  two  parts  and  a 
half  of  chalkj  a  very  good  hydraulic  lime  may  be  made.  He  concludes  from 
many  experiments,  that  a  limestone  containing  six  per  cent,  of  clay,  affords  a 
mortar  perceptibly  hydraulic.  Lime  containing  from  fifteen  to  twenty  per 
cent.,  is  very  hydraulic,  and  with  from  twentyfive  to  thirty  ^er  cent.,  it  sets 
almost  instantly. 

According  to  M.  Bruyere,  an  excellent  artificial  puzzolana  may  be  formed 
by  heating  together  three  parts  of  clay,  and  one  part  of  slaked  lime,  for  some 
hours,  to  redness. 

t  M.  Vicat,  who  has  experimented  extensively  upon  the  subject,  has  arriv- 
ed at  the  conclusion,  that  the  solidification  of  hydraulic  cements  formed  of  or- 
dinary mortar,  and  calcined  clays,  is  the  result  of  a  true  chemical  combination, 
in  which  the  lime  is  neutralized  by  the  silica  and  alumina.  But  in  those 
formed  of  hydraulic  lime  and  pure  sand,  the  solidification  does  not  appear  to 
result  from  chemical  combination. 

Clays  which  by  slight  calcination  become  good  hydraulic  cements,  have 
also  the  same  property,  though  in  a  less  degree,  in  their  natural  state.  It  has 
been  asserted,  by  M.  Treussart,  that  the  free  access  of  air  during  the  calcina- 
tion of  argillaceous  cements,  is  of  great  consequence  to  the  tenacity  of  the 
mortar  and  the  quickness  with  which  it  hardens.  To  determine  whether  a 
stone  will  furnish  hydraulic  lime,  M.  Vicat  recommends  to  calcine  it  by  heat, 
then  to  slake  it  in  the  common  way,  and  make  a  paste  of  it,  which  is  to  be 
placed  at  the  bottom  of  a  vessel  of  pure  water.  If  at  the  end  of  eight  or  ten 
days  it  has  become  hard  and  resists  the  finger,  it  will  furnish  hydraulic  lime  ; 
but  if  it  remains  soft,  it  has  the  character  of  common  lime. 

See  Brando's  Journal,  vol.  x,  p.  407. — vol.  xix,329. — vol.  xx,  50. — vol.  xxii, 
214.    Also  Franklin  Journal,  ii,  371  and  287.— iii.,  305,  355. 


MATERIALS  USED   IN  THE  ARTS. 


19 


afforded,  both  to  the  ancients  and  moderns,  cements  of  great 
hardness  and  permanency,  but  they  are  not  much  used. 

Metals. — Iron. — Of  all  the  metals  iron  is  the  most  useful, 
and  one  of  the  most  abundantly  diffused.  Besides  its  common 
occurrence  in  earths  and  rocks,  it  is  held  in  solution  by  mineral 
waters,  it  enters  largely  into  the  composition  of  meteoric  stones, 
and  it  circulates  in  the  blood  of  animals,  and  the  sap  of  vege- 
tables. Pure  iron  is  of  a  bluish  white  color,  of  great  hardness, 
malleable,  ductile,  and  tenacious.  For  its  fusion,  it  requires  an 
intensely  high  temperature,  equal  to  one  hundred  and  fiftyeiglit 
degrees  of  Wedgewood's  pyrometer.  When  combined  with 
carbon  it  forms  steely  and  is  increased  in  hardness.  At  a  red 
heat,  it  becomes  soft  and  more  malleable  ;  and  at  a  white  heat, 
may  be  joined  by  welding.  It  is  strongly  attracted  by  the  mag- 
net, acquires  itself  the  magnetic  power,  and  when  in  the  form 
of  steel,  retains  it  permanently.  Cast  iron  is  brittle,  and  fusible 
without  difficulty,  owing  to  the  carbon  which  it  contains. 
Wrought  iron  is  flexible,  and  has  the  properties  of  the  pure 
metal.  In  the  arts,  iron  is  applied  to  innumerable  uses  where 
strength  and  hardness  are  required.  It  is,  however,  deficient 
in  durability,  being  readily  corroded  with  rust,  when  exposed 
to  the  weather,  unless  protected  with  a  coating  of  paint.  Me- 
tallic iron  is  wrought,  while  hot,  by  hammering,  rolling,  stamp- 
ing, chiselling,  punching,  &ic. ;  and  when  cold,  by  the  same 
means,  also  by  filing,  turning,  drilling,  cutting,  and  drawing. 
Cast  iron  is  commonly  melted,  when  its  form  is  to  be  changed  ; 
but  it  is  finished  with  common  tools  when  cold,  and  may  be  cut 
with  a  saw  when  red  hot.  Cast  iron  is  now  the  most  common 
material  used  in  the  fabrication  of  machines,  and  in  Europe  it 
is  applied  to  the  construction  of  bridges,  and  of  roofs.  Even 
ships  have  been  made  of  iron. 

To  the  chemical  compounds  of  iron,  we  are  indebted  for 
copperas,  writing  ink,  prussian  blue,  &:c. 

Copper. — Copper  is  a  metal  of  alight  red  color,  ductile,  and 
malleable,  emitting  a  disagreeable  odor  when  rubbed.  It  melts 
at  twentyseven  degrees  of  Wedgewood.    When  exposed  to  the 


20 


MATERIALS  USED  IN  THE  ARTS. 


atmosphere  it  loses  its  lustre  and  becomes  covered  with  a  green 
coating,  which  is  carbonate  of  copper.  This  coating  preserves 
the  remainder  from  decay,  and  is  the  source  of  some  of  its 
most  important  uses.  Copper  is  employed  to  cover  the  bottoms 
of  ships,  and  tops  of  houses  ;  to  form  various  culinary  and  manu- 
facturers' vessels,  also  for  pumps,  and  water  pipes,  for  engravers' 
plates,  and  for  coining.  When  combined  with  acids,  or  oxygen, 
it  becomes  more  or  less  poisonous,  on  which  account  culinary 
vessels  are  coated  on  the  inside  with  tin.  It  is  this  poisonous 
property,  in  part,  which  prevents  marine  animals  from  attaching 
themselves  to  the  bottoms  of  coppered  ships.  Copper  forms 
many  valuable  alloys,  among  which  are  hrass^  which  consists  of 
copper  and  zinc,  and  bronze,  which  is  made  of  copper  and 
tin.  Its  chemical  compounds  furnish  verdigris,  blue  vitriol,  &;c. 
It  is  wrought  by  the  same  modes  as  iron,  but  is  more  easily 
malleable  than  that  metal  when  cold. 

Lead. — Lead  has  a  light  bluish  color,  with  a  bright  lustre 
which  becomes  quickly  tarnished  on  exposure  to  the  air.  It  is 
soft,  heavy,  very  malleable,  and  melts  at  six  hundred  degrees  of 
Fahrenheit's  thermometer.  By  exposure  to  the  heat  of  a  fur- 
nace, it  is  converted  into  a  red  oxide.  Lead  is  used  for  the  cover- 
ing of  roofs,  for  aqueducts,  for  hning  cisterns  and  tight  cavities, 
for  weights,  bullets,  and  shot.  Some  of  its  alloys  are  very  val- 
uable, such  as  pewter,  type  metal,  he.  Its  oxides  and  salts 
afford  paints  of  different  colors,  and  of  great  use.  Lead  is  de- 
leterious in  its  influence  on  health,  and  requires  great  caution 
in  those  who  work  it,  or  use  it,  in  any  other  than  the  metallic 
state.  Injury  is  most  frequently  received,  by  inhaling  the  dust 
which  rises  in  the  manufactories  of  red,  and  white  lead.  In 
leaden  aqueducts  a  carbonate  of  lead  occasionally  forms  ;  but 
this  is  insoluble  in  water,  and  subsides  by  its  weight. 

Tin. — Tin  is  a  white  metal,  somewhat  harder  than  lead,  and 
producing  a  peculiar  crackling  sound  when  it  is  bent.  It  is 
very  malleable,  and  is  beaten  for  tinfoil  into  leaves  y^\j-^  part  of 
an  inch  in  thickness.  Its  ductility  and  tenacity  are  not  great. 
Tin  is  very  fusible,  melting  at  about  four  hundred  and  fortytwo 


MATERIALS  USED  IN  THE  ARTS. 


21 


degrees  of  Fahrenheit's  thermometer.  Exposed  to  the  atmos- 
phere its  surface  becomes  slightly  tarnished,  but  undergoes  no 
further  change.  On  this  account  it  is  largely  employed  for  coat- 
ing other  metals,  which  are  more  liable  to  oxidation.  Copper 
vessels  are  lined  with  it,  as  already  stated.  Tin  plates  are  sheets 
of  iron  coated  with  tin.  Tinfoil  with  mercury  forms  the  silvering 
of  looking  glasses.  Block  tin  is  used  to  form  vessels  not  intend- 
ed for  exposure  to  heat.  Some  of  the  salts  of  tin  are  very  val- 
uable in  dyeing.  The  putty  used  for  polishing  glass,  stones,  and 
metals,  is  an  oxide  of  lead  and  tin. 

Mercury. — Mercury,  or  quicksilver,  is  fluid  at  common  tem- 
peratures, and  on  this  account  is  used  in  many  philosophical 
and  chemical  instruments.  Attempts  have  been  made  to  intro- 
duce it  in  certain  forms  of  the  steam  engine  ;  but  it  is  objec- 
tionable for  this  purpose,  from  its  tendency  to  combine  with  ox 
ygen,  and  from  the  unhealthiness  of  its  use  to  persons  occupied 
about  it.  Mercury  is  employed  in  silvering  mirrors,  and  large 
quantities  are  consumed  in  extracting  silver  and  gold  from  their 
ores.  Its  alloys  with  other  metals,  are  called  amalgams.  It 
amalgamates  readily  with  gold,  silver,  tin,  lead,  and  zinc  ;  diffi- 
cultly with  copper  and  antimony,  and  scarcely  at  all  with  iron 
and  platina. 

Gold. — The  value  derived  from  its  scarcity,  prevents  the 
extensive  use  of  gold  in  the  arts.  The  power  with  which  it 
resists  tarnishing,  and  all  changes  from  exposure  to  air  and 
moisture,  renders  it  desirable  for  many  purposes,  and  has  giv- 
en rise  to  the  art  of  gilding.  The  gold  leaf  used  in  gilding  is 
often  not  more  than  ^•g-aiw  P^^^  ^f  an  inch  thick,  owing  to  the 
extreme  malleability  of  the  metal.  Gold  is  used  in  coining,  in 
jewelry,  and  in  coloring  porcelain. 

Silver. — Silver  possesses  the  same  valuable  properties  as 
gold,  but  is  more  liable  to  tarnish,  especially  when  exposed  to 
sulphurous  vapors,  which  convert  its  surface  into  a  sulphuret. 
Silver  is  very  ductile,  but  less  so  than  gold,  and  the  leaves  into 
which  it  is  hammered,  are  usually  three  times  thicker  than  those, 
of  gold.    Its  uses  are  well  known. 


22 


MATERIALS  USED  IN  THE  ARTS. 


Platinum. — Platinum  is  tlie  heaviest  substance  at  present 
known,  its  weight  being  twentyone  times  and  a  half,  that  of 
Avater.  Like  gold,  it  resists  tarnishing  from  oxidation  by  the 
air,  and  it  is  furthermore  capable  of  resisting  an  extremely  high 
temperature  without  mehing.  It  is  very  malleable,  approaches 
to  iron  in  hardness,  and  hke  that  metal,  may  be  welded  when 
hot.  It  is  used  for  small  crucibles,  and  philosophical  instru- 
ments. 

Zinc. — Zinc  or  spelter  is  a  bluish  white  metal,  imperfectly 
malleable  and  ductile,  but  rendered  more  so  by  a  heat  some- 
what above  that  of  boiling  water.  It  melts  below  a  red  heat, 
at  seven  hundred  degrees  of  Fahrenheit.  When  ignited  it  burns 
with  a  white  flame,  throwing  off  an  oxide  called  ^oii^e?**  of  zinc. 
Zinc  is  used  as  a  constituent  in  brass,  and  in  some  other  alloys. 
It  is  an  important  material  in  galvanic  combinations.  It  is  easily 
oxidated,  and  therefore  unfit  for  purposes  which  require  dura- 
bility. 

Antimony. — Antimony  is  a  brittle,  whitish  metal  of  a  plated 
or  scaly  texture.  It  is  tarnished,  but  not  otherwise  altered  by 
exposure  to  the  air.  In  type  founderies  it  is  much  used  to  give 
hardness  to  lead,  in  the  alloy  called  type  metal. 

Bismuth. — Bismuth  is  a  metal  of  a  reddish  white  color  and 
brittle  consistence,  not  readily  oxidated  by  the  air.  It  is  very 
fusible,  requiring  little  more  heat  than  tin  to  melt  it.  It  enters 
into  various  alloys,  one  of  which  is  the  fusible  metal,  compos- 
ed of  eight  parts  of  bismuth,  five  of  tin,  and  three  of  lead, 
which  melts  at  a  heat  less  than  that  of  boiling  water. 

Arsenic. — Arsenic  in  its  metalHc  state  is  of  a  bluish  white 
color,  easily  tarnishing,  brittle,  and  volatile  at  a  low  heat.  In 
the  state  of  acid,  called  white  arsenic,  it  is  well  known  as  a  vio- 
lent poison.  Arsenic  is  used  in  the  manufactures  of  glass,  and 
of  shot,  and  furnishes  the  basis  of  several  brilhant  pigments. 

Manganese. — Manganese  is  a  metal  of  a  dull  whitish  color, 
brittle,  extremely  difficult  to  melt,  and  speedily  turning  to  a 
dark  oxide  in  the  air.  The  native  black  oxide  of  this  metal  is 
of  great  use  to  chemists  in  furnishing  oxygen.  In  the  arts,  it 
is  employed  in  bleaching,  pottery,  and  glass  making. 


MATERIALS  USED   IN  THE  ARTS. 


Combustible  substances,  he. — Bitumen. — This  is  an  in- 
flammable mineral  substance,  resembling  tar  or  pitch  in  its  prop- 
erties and  uses.  Among  different  bituminous  substances,  the 
names  naphtha,  and  petroleum,  have  been  given  to  those  which 
are  fluid  ;  maltha,  to  that  which  has  the  consistence  of  pitch, 
and  asphaltum,  to  that  which  is  solid. 

Amber. — Amber  is  a  yellowish,  translucent,  inflammable 
mineral,  hard  enough  to  receive  a  fine  polish,  capable  of  be- 
ing wrought  into  various  ornamental  articles,  and  forming  an  in- 
gredient in  some  varnishes  and  lacquers. 

Coal. — This  well  known  combustible  is  composed  essential- 
ly of  carbon,  with  a  proportion,  greater  or  less,  of  bitumen,  a 
little  sulphur,  and  a  remainder  of  earthy  and  incombustible  matter. 
True  coal  burns  with  a  white  flame,  a  black  smoke  and  bitu- 
minous odor.  Some  kinds,  as  the  Cannel  coal,  burn  readily, 
with  a  large  flame,  and  without  softening  or  concreting.  Oth- 
ers, as  the  Newcastle,  Liverpool,  and  Orrel,  concrete,  or  cake, 
during  combustion,  and  last  longer.  The  poorer  coals  have 
usually  a  large  admixture  of  foreign  and  incombustible  sub- 
stances. Coal  is  of  great  value  as  a  fuel,  both  in  the  arts,  and 
for  domestic  purposes.  As  it  contains  more  combustible  mat- 
ter in  a  given  volume,  than  wood,  it  is  capable  of  evolving  and 
sustaining  more  heat  than  that  fuel,  within  the  same  furnace,  or 
other  cavity.  When  coal  is  exposed  to  heat,  but  prevented 
from  burning,  by  the  exclusion  of  the  air,  it  loses  its  moisture 
and  bituminous  portion,  and  is  converted  into  coke,  a  fuel  bear- 
ing the  same  relation  to  coal,  as  charcoal  to  wood.  Coal  has 
of  late  years  been  usefully  applied  to  the  production  of  inflam- 
mable gas,  for  the  purposes  of  illumination. 

Anthracite. — This  combustible,  of  which  the  Lehigh, 
Schuylkill,  and  Rhode  Island  coal  are  specimens,  is  harder, 
heavier,  and  less  black,  than  the  true,  or  butuminous  coals.  It 
burns  slowly,  without  smoke,  and  with  a  faint  flame.  It  is  more 
difficult  to  kindle  than  most  fuels,  owing  to  its  greater  conducting 
power,  and  the  high  temperature  necessary  for  its  combustion ; 
but  when  once  on  fire  it  produces  an  intense  and  lasting  heat. 


24 


MATERIALS  USED  IN  THE  ARTS. 


It  is  more  durable  than  the  bituminous  coals,  but  requires  to  be 
burnt  in  masses  large  enough  to  sustain  a  high  temperature.  An- 
thracite has  now  become  a  common  fuel  in  many  parts  of  the 
United  States,  and  is  highly  valuable  both  for  domestic  and  man- 
ufacturing purposes.  It  is  burnt  in  various  furnaces,  forges, 
stoves,  and  grates  constructed  for  the  purpose.  In  iron  works 
it  is  found  to  occasion  less  oxidation  and  scaling  of  the  metal, 
than  other  fuel.  But  in  reverberating  furnaces,  where  a  blaze 
is  required,  it  does  not  answer  the  requisite  purpose.  Most  of 
the  anthracites  afford  inflammable  gas,  not,  however,  suitable 
for  purposes  of  illumination.* 

Graphite. — This  mineral,  otherwise  called  plumbago  and 
black  lead,  is  composed  of  carbon,  with  a  portion  of  iron.  It 
is  unctuous  to  the  touch  and  soils  the  fingers.  It  is  used  for 
pencils  and  crayons,  and,  mixed  with  clay,  is  formed  into  cru- 
cibles. Black  lead  pencils  are  made,  by  inserting  the  straight 
edge  of  a  plate  of  graphite,  into  a  groove  made  in  the  wood, 
and  sawing  it  off,  leaving  a  slender  rod  of  the  lead  inclosed, 
which  is  afterwards  covered  with  wood. 

Peat, — Peat  is  a  substance  of  vegetable  origin,  dug  from 
bogs  and  marshes,  and  capable  of  reproducing  itself  in  places 
from  which  it  has  been  removed.  Peat,  when  dry,  is  combusti- 
ble, and  is  used  as  such,  where  better  fuel  cannot  be  obtained. 

Sulphur. — Sulphur  is  a  simple  inflammable  body,  melting  at 
two  hundred  and  twenty  degrees,  and  taking  fire  at  five  hun- 
dred, of  Fahrenheit.  When  kept  melted  for  some  time,  at 
about  three  hundred  degrees,  Fahrenheit,  it  becomes  thick  and 
viscid,  and  if  poured  into  a  basin  of  water,  it  becomes  ductile  like 
wax.  In  this  state  it  is  used  for  taking  impressions  of  seals. 
It  is  also  used  to  form  moulds  for  plaster  casts.  Sulphur  is  an 
ingredient  in  gunpowder,  and  enters  into  many  chemical  com- 
pounds, which  are  of  great  use  in  the  arts.  Sulphur  is  burnt 
to  produce  sulphuric  acid. 

*  See  a  valuable  paper  on  the  Anthracites,  in  Silliman's  Journal,  vol.  x.  p. 
831,  by  the  editor. 


MATERIALS  USED  IN  THE  ARTS. 


25 


MATERIALS  FROM  THE   VEGETABLE  KINGDOM. 

Wood. — The  woody  portion  of  the  trunks  of  trees,  is  made 
up  of  minute  tubes  or  vessels,  running  longitudinally,  having 
their  parietes  strengthened  with  rigid  fibres,  and  their  intersti- 
ces filled  with  cellular  substance.  In  the  common  trees  of 
temperate  climates,  these  vessels  are  arranged  in  concentric 
layers  or  cylinders ;  one  layer  being  added  for  each  year  of 
the  tree's  growth.  The  outer  layers,  being  those  which  trans- 
mit the  sap,  are  more  porous,  soft  and  perishable,  and  are 
known  by  the  name  of  alburnum  or  sap  wood.  The  inner  lay- 
ers are  commonly  darker  colored,  more  solid,  compact,  and  du- 
rable ;  and  are  known  by  the  name  of  heart  wood.  The  heart 
wood  is  preferred  for  most  purposes  in  the  arts,  its  vessels  hav- 
ing become  in  part  obliterated  by  age,  and  its  density  and 
strength  increased.  Boards  are  least  Hable  to  warp  when  they 
are  cut  through  the  centre  or  pith  of  the  trunk.  All  wood 
shrinks  in  drying,  and  decays  when  exposed  to  the  weather ; 
but  the  different  trees  vary  greatly  from  each  other  in  this 
respect. 

Bark. — Bark  is  the  external  investment  of  the  trunks  and 
branches  of  trees,  and  consists,  when  young,  of  three  coats  or 
layers,  called  the  cuticle,  the  cellular  integument,  and  the  liber 
or  inner  bark.  But  during  every  season,  a  new  liber  grows  on 
the  inside  of  the  former  ones,  and  pushes  them  outward,  so  that 
old  bark  is  found  to  consist  of  numerous  cortical  layers,  each 
of  which  was  originally  a  liber.  The  outermost  of  these  lay- 
ers gradually  become  dead  and  dry,  and  merely  augment  the 
thickness  of  the  bark,  without  adding  to  its  usefulness  in  the 
arts. 

OaJc. — Numerous  species  of  the  oak  tree  are  found  in  the 
United  States.  They  are  generally  distinguished  for  great 
strength,  but  are  coarse  grained,  and  prone  to  warp  and  crack 
under  changes  from  moisture  to  dryness.  The  live  oak  of  the 
Southern  States  ( Quercus  virens)  is  prized  in  ship  building,  be- 
4 


MATERIALS  USED  IN  THE  ARTS. 


yond  any  native  timber.  The  white  oak  ( Qaercus  alba)  is  em- 
ployed for  the  keels,  side  timbers,  and  planks  of  vessels,  also 
for  frames  of  houses,  mills  and  machinery  requiring  strength  ; 
for  wagons,  parts  of  carriages,  ploughs,  and  other  agricultural 
instruments.  Large  quantities  are  consumed  for  the  staves  and 
hoops  of  casks,  for  which  they  furnish  one  of  the  best  materi- 
als. The  bark  of  the  black  oak  ( Quercus  tinctoria)  furnishes 
the  quercitron  used  by  dyers.  Most  of  the  species  of  oak  are 
employed  in  tanning,  and  they  all  furnish  a  valuable  fuel. 

Hickory  or  Walnut. — The  wood  of  the  different  species  of 
native  walnut  or  hickory  (Juglans,  seu  Carya)  is  eminently  dis- 
tinguished for  weight,  tenacity,  and  strength.  It  has,  however, 
important  defects.  It  warps  and  shrinks  greatly,  decays  rap- 
idly when  exposed  to  the  weather,  and  is  very  liable  to  the  at- 
tacks of  worms.  On  these  accounts  it  is  never  used  for  house  or 
ship  building,  but  is  chiefly  employed  for  minor  purposes,  where 
strength  is  the  chief  requisite ;  as  in  the  teeth  of  rtiill  wheels, 
screws  of  presses,  handspikes,  capstan  bars,  bows,  hoops,  and 
handles  of  tools.  As  fuel,  the  hickory  stands  at  the  head  of 
native  trees,  and  commands  a  higher  price  than  any  other 
wood. 

Ash. — The  white  ash  (Fraocinus  Americana)  and  some  oth- 
er species,  are  of  great  utility  in  the  arts.  Ash  wood  is  strong, 
elastic,  tough,  and  light ;  and  splits  with  a  straight  grain.  It  is 
also  durable,  and  permanent  in  its  dimensions.  It  furnishes 
the  common  timber  used  in  hght  carriages,  for  the  shafts,  frames, 
springs,  and  part  of  the  wheels.  Flat  hoops,  boxes,  and  the 
handles  of  many  instruments  are  made  of  it.  It  is  almost  the 
only  material  of  oars,  blocks  of  pullies,  cleats,  and  similar  naval 
implements,  in  places  where  it  can  be  obtained. 

Elm.— The  common  American  elm  ( Ulmus  Americana)  is 
valued  for  the  toughness  of  its  wood,  which  does  not  readily 
split.  On  this  account  it  it  chiefly  used  for  the  naves,  among 
us  commonly  called  hubbs,  of  carriage  wheels. 

Locust. — The  common  locust  [Robinia  pseudacacia)  is  one 
of  the  hardest,  strongest,  and  most  valuable  of  native  trees. 


MATERIALS  USED  IN  THE  ARTS. 


27 


The  larger  pieces  of  its  timber,  are  used  in  ship  building,  and 
the  smaller  pieces  are  in  great  request  to  form  the  treenails*  or 
pins  which  confine  the  planks  to  the  timbers.  This  tree  is  lia- 
ble, in  the  Northern  States,  to  be  perforated  by  an  insect,  so  that 
it  is  often  difficult  to  procure  sound  pieces  of  any  considerable 
size.  Locust  wood  is  exceedingly  durable,  when  exposed  to 
the  weather  ;  and  forms  excellent  fuel. 

fVild  Cherrytree. — The  wood  of  this  tree  [Prunus  T^irgini- 
ana)  is  of  a  deep  color,  hard,  durable,  and,  when  properly  sea- 
soned, very  permanent  in  its  shape  and  dimensions.  In  the 
manufacture  of  cabinet  work,  it  is  much  used  as  a  cheaper 
substitute  for  mahogany.  On  the  Western  rivers  it  is  sometimes 
used  in  ship  building. 

Chesnut. — The  American  chesnut  {Castanea  vescaB.)  is  a 
large  tree  of  rapid  growth.  Its  wood  is  coarse  and  porous, 
very  liable  to  warp,  and  seldom  introduced  into  building  or  fur- 
niture. It  is  chiefly  used  for  fencing  stuff,  to  which  use  it  is 
fitted  by  its  durability  in  the  atmosphere.  Chesnut  is  an  unsafe 
fuel,  in  consequence  of  its  tendency  to  snap  and  thi'ow  its  coals 
to  a  distance. 

Beech. — The  wood  of  the  red  beech  (Fagus  ferruginea)  is 
liable  to  decay  when  exposed  to  ahernate  moisture  and  dry- 
ness. It  does  not,  however,  readily  warp,  and  being  smooth 
grained  it  is  used  for  some  minor  purposes,  such  as  the  mak- 
ing of  planes,  lasts,  and  card  backs.  It  forms  a  very  good 
fuel. 

Basswood. — The  American  linden  or  basswood  tree  [Tilia 
Americana)  produces  a  fine  grained  w^ood,  w^hich  is  very  white, 
soft,  light,  and  flexible.  It  is  sometimes  employed  for  furni- 
ture, but  its  chief  use  is  to  form  the  pannels  of  coach  and  chaise 
bodies,  for  which  its  flexibility  makes  it  well  suited. 

Tulip  tree. — {Liriodendron  tuJipifera.)  The  boards  of  this 
tree  are  sold  under  the  name  of  white  wood,  and  erroneously 
under  that  of  poplar.  Its  wood  is  smooth,  fine  grained,  easily 
vvi'ought,  and  not  apt  to  split.    It  is  used  for  carving  and  orna- 

^  Commonly  pronounced  trunnels. 


38 


MATERIALS  USED  IN  THE  ARTS. 


mental  work,  and  for  some  kinds  of  furniture.  In  the  Western 
States,  where  pine  is  more  scarce,  the  joinery,  or  inside  work 
of  houses,  is  commonly  executed  with  this  material,  and  some- 
times the  outer  covering.  In  common  with  basswood,  it  forms 
an  excellent  material  for  coach  and  chaise  pannels. 

Maple. — The  rock  maple,  {Acer  saccharinum)  also  several 
other  species,  affords  wood  which  is  smooth,  compact  and  hard. 
It  is  much  used  for  cabinet  furniture,  and  is  a  common  material 
for  gunstocks.  The  wood  in  some  of  the  old  trunks,  is  full  of 
minute  irregularities,  like  knots.  These,  if  cut  in  one  direc- 
tion, exhibit  a  spotted  surface,  to  which  the  name  of  bird's  eye 
maple  is  given  ;  while  if  cut  in  another  direction,  they  produce 
a  wavy  or  shaded  surface,  called  curled  maple.  This  last  ef- 
fect, however,  is  more  frequently  produced  by  a  mere  serpen- 
tine direction  of  the  fibres.  The  distinctness  of  the  grain  may 
be  increased  by  rubbing  the  surface  with  diluted  sulphuric  acid. 
Maple  wood  forms  a  good  fuel.  It  is  not  very  lasting  when 
exposed  to  the  weather.  The  sap  of  the  rock  maple  and  of 
one  or  two  other  species,  yields  sugar  on  being  boiled. 

Birch. — The  white  or  paper  birch  [Betula  papyracea)  has 
properties  similar  to  those  of  the  maple,  and  is  appropriated  to 
the  same  uses.  Its  cuticle  or  outer  bark,  is  made  by  the  In- 
dians into  canoes.  The  lesser  white  birch  [B.  populifolia)  is 
a  perishable  tree,  of  litde  value.  The  black  birch,  [B.  lenta,) 
known  for  its  aromatic  bark,  affords  a  firm,  compact,  dark  col- 
ored wood,  much  valued  for  furniture,  and  sometimes  used  for 
screws  and  implements  requiring  strength.  The  yellow  birch 
[B.  lutea)  is  applied  to  the  same  uses  as  the  last;,  and  makes 
good  fuel. 

Buttonwood. — The  buttonwood  or  plane  tree  {Platanm  oc- 
cidentalis)  is  in  some  of  the  Northern  States  improperly  called 
sycamore.  It  is  one  of  the  largest  inhabitants  of  the  forest, 
and  Michaux  states  that  trees  are  found  in  the  Western  States 
which  measure  forty  feet  in  circumference.  This  majestic  tree 
is  chiefly  valuable  for  its  shade,  as  the  wood  is  perishable,  and 
prone  to  warp. 


MATERIALS  USED  IN  THE  ARTS. 


Persimmon. — {Diospyros  Virginiana.)  The  heart  wood 
is  dark  colored,  compact,  hard,  and  elastic  ;  and  is  used  in  the 
Southern  States  for  screws,  shafts  of  chaises,  and  various  im- 
plements. 

Black  Walnut. — [Juglans  nigra.)  This  tree  is  rarely  found 
north  of  New  York.  Its  heart  wood  is  of  a  violet  color,  which 
after  exposure  to  the  air,  assumes  a  darker  shade,  and  finally 
becomes  nearly  black.  This  wood  when  deprived  of  its  white 
part,  or  sap,  remains  sound  for  a  long  time,  even  if  exposed  to 
air  and  moisture,  and  is  not  attacked  by  worms.  It  is  very 
strong  and  tenacious,  and  when  seasoned  is  not  liable  to  warp, 
or  split.  It  is  used  in  the  Middle  and  Western  States  for  fur- 
niture, for  gunstocks,  for  naves  of  wheels,  and  to  a  certain  ex- 
tent, in  house  and  ship  building. 

Tupelo. — Different  species  of  the  genus  JVyssa  have  receiv- 
ed in  the  United  States,  a  great  variety  of  common  names, 
among  which  tupelo,  pepperidge,  and  gum  tree  are  the  most 
common.  In  Massachusetts  the  name  hornbeam  is  improperly 
applied  to  one  of  them.  Their  wood  is  smooth  grained,  and 
remarkable  for  the  decussation  or  interweaving  of  the  fibres, 
which  renders  it  almost  im.possible  to  split  the  logs.  This 
quality  causes  several  of  the  species  to  be  in  demand  for  naves 
of  wheels,  hatters  blocks,  and  implements  requiring  lateral 
tenacity. 

Pine. — The  American  pines  exceed  all  other  native  trees 
for  the  value  and  variety  of  their  uses.  The  white  pine  (Pinus 
strobus)  has  a  very  tall,  straight  trunk,  the  wood  of  which  is 
light,  soft,  homogeneous,  and  easy  to  work.  It  is  remarkably 
exempt  from  the  common  fault  of  timber,  that  of  decaying  in 
the  open  air,  and  of  changing  its  dimensions  with  changes  of 
weather.  On  these  accounts  it  is  extensively  employed  for 
most  of  the  common  purposes  of  timber.  In  the  Northern 
States,  masts  of  vessels  are  commonly  made  of  it.  Frames  of 
houses,  and  of  bridges  are  also  formed  of  it ;  its  defect  of 
strength  being  more  than  balanced  by  its  steadiness  and  dura- 
bility.   Its  boards  form  almost  the  only  material  used  in  the 


30, 


MATERIALS  USED  IN  THE  ARTS. 


Northern  States  for  the  joiner's  work,  or  inside  finishing  of 
houses  ;  and  for  this  use  it  is  exported  to  other  countries.  Or- 
namental carving  is  commonly  executed  in  this  material.  The 
southern  pitch  pine  {Pinus  palustris  L.)  covers  extensive  bar- 
rens in  the  Southern  States,  and  yields  vast  quantities  of  tar 
and  turpentine.  Its  wood  is  appropriated  to  the  same  objects 
as  that  of  the  white  pine,  but  is  harder  and  stronger,  and  there- 
fore preferred  for  planks,  spars,  floors,  decks,  &ic.  Many  oth- 
er species  of  pine  exist  on  this  continent,  partaking  qualities 
like  those  already  described,  but  most  of  them  harder  than  the 
white  pine. 

Spruce. — The  black  and  white  spruce,  belong  to  the  race  of 
trees  commonly  called  Firs.  They  are  both  valuable,  but  the 
black  spruce  {Pinus  nigra)  unites  in  a  peculiar  degree  the 
qualities  of  strength,  elasticity,  and  lightness,  together  with  the 
power  of  resisting  exposure  to  the  weather.  It  is  much  sought 
after  for  the  smaller  spars  of  vessels,  such  as  the  booms,  yards, 
and  topmasts. 

Hemlock. — The  hemlock  tree  [Pinus  Canadensis)  is  inferi- 
or to  the  other  firs  in  quality,  though  it  grows  to  a  large  size. 
It  is  coarse  grained,  often  twisted,  and  cracks  and  shivers  with 
age.  It  furnishes  an  inferior  sort  of  boards,  used  in  covering 
houses.    Its  bark  is  valuable  in  tanning. 

White  Cedar. — This  tree  [Cupressus  thuyoides)  occupies 
large  tracts  denominated  cedar  swamps.  The  wood  is  soft, 
smooth,  of  an  aromatic  smell,  and  internally  of  a  red  color.  It 
is  permanent  in  shape,  and  very  durable  ;  and  esteemed  as  a 
material  for  fences.  Large  quantities  of  shingles  are  made  of 
it.  It  is  a  favorite  material  for  wooden  wares,  or  the  nicer  kinds 
of  cooper's  work. 

Cypress. — The  cypress  tree  of  the  Southern  States  (Cii- 
pressus  disticha)  is  light,  soft,  and  fine  grained  ;  and  at  the  same 
time  elastic,  with  a  considerable  share  of  strength.  It  sustains 
heat  and  moisture  for  a  long  time,  without  injury.  In  the 
Southern  States  and  on  the  Mississippi,  it  is  much  employed 
for  fences,  and  for  the  frames,  shingles,  and  inside  work  of 
houses. 


MATERIALS  USED  IN  THE  ARTS. 


31 


Larch. — The  American  Larch  (Pinus  ndcrocarpa)  is  called 
hackmatack  and  tamarack,  in  different  parts  of  the  Union. 
Its  wood  is  strong,  elastic,  and  durable  ;  and  is  highly  prized,  in 
places  where  a  sufficient  quantity  can  be  obtained,  for  naval 
and  civil  architecture. 

Arbor  Vito^. — This  tree  ( Thuya  occidentalis)  is  of  the  mid- 
dle size,  and  frequently  called  white  cedar.  The  wood  is 
reddish,  fine  grained,  very  soft,  and  light.  It  bears  exposure 
to  the  weather  with  very  little  change,  and  is  esteemed  for  the 
posts  and  rails  of  fences. 

Red  Cedar. — [Juniperus  Virginiana.)  The  name  of  5am7i 
is  in  some  places  improperly  applied  to  this  tree.  Unlike  the 
white  cedar,  it  grows  in  the  driest  and  most  barren  soils.  The 
trunk  is  straight,  and  knotted  by  small  branches.  The  heart 
wood  is  of  a  bright  red  color,  smooth  and  moderately  soft.  It 
exceeds  most  other  native  trees  in  durability,  and  is  in  particular 
request  for  posts  of  buildings,  though  it  is  difficult  to  obtain  it 
of  large  size. 

Willoio. — The  most  common  kinds  of  Salix  or  willow  about 
our  seaports,  are  European  species  which  have  become  natur- 
alized. Their  wood  is  soft,  light,  and  spongy.  Willow  char- 
coal is  used  in  the  manufacture  of  gunpowder.  The  osier  and 
some  other  species,  with  long  slender  shoots,  are  extensively 
cultivated  to  form  wicker  work,  such  as  baskets,  hampers,  and 
the  external  coverings  of  heavy  glass  vessels. 

Mahogany. — In  the  manufacture  of  cabinet  furniture,  ma- 
hogany [Swietenia  mahagoni)  has  taken  precedence  of  all 
other  kinds  of  wood.  Its  value  depends  not  so  much  on  its 
color,  as  on  its  hardness,  and  the  invaluable  property  of  remain- 
ing constant  in  its  dimensions,  without  warping  or  cracking,  for 
an  indefinite  length  of  time.  The  same  qualities  which  render 
it  suitable  for  furniture,  have  given  rise  to  its  employment  for 
the  frames  of  philosophical  instruments,  and  of  delicate  ma- 
chinery. Mahogany  is  imported  from  the  West  Indies,  and 
different  parts  of  Spanish  America. 


32 


MATERIALS  USED  IN  THE  ARTS. 


Boxwood. — The  box  tree  [Buxus  sempervirens)  is  imported 
from  the  south  of  Europe.  Its  wood  is  of  a  well  known  yel- 
lowish color,  hard,  compact,  smooth,  tough,  and  not  liable  to 
crack.  Musical  wind  instruments  are  commonly  made  of  it ; 
also  mathematical  measuring  instruments.  The  handles  of  many 
tools,  and  various  articles  of  turners'  work,  consist  also  of  this 
material.  Wood  engravings  are  cut  upon  the  end  of  the  grain 
of  boxwood. 

Lignum  Vitce. — The  wood  of  the  Guiacum  officinale  is  em- 
ployed in  the  arts  under  this  name.  It  is  dark  colored  at  the 
heart,  strong,  exceedingly  hard,  and  so  heavy  as  to  sink  in  wa- 
ter. It  is  impregnated  with  resin,  and  on  this  account  durable 
in  liquids.  Handles  of  tools,  boxes  of  gudgeons,  wheels  of 
puUies,  castors,  balls,  stopcocks,  mallets,  &c.,  are  made  of  it. 
It  is  imported  from  the  West  Indies,  and  South  America. 

Several  other  tropical  woods  are  imported  for  use  by  cabinet 
makers,  such  as  rose  wood,  ebony,  satin  wood,  he.  They  are 
generally  hard,  colored  woods,  susceptible  of  a  fine  polish. 
Satin  wood  [Sweitenia  chloroxylon)  is  thought  poisonous  to  the 
hands  of  the  workmen. 

Cork. — Cork  is  a  fungous  substance  growing  on  the  bark  of 
a  species  of  oak  ( Quercus  suber)  in  the  south  of  Europe.  Its 
lightness  and  elasticity  gives  it  an  aptitude  for  certain  purposes, 
in  which  it  would  be  difficult  to  find  a  substitute. 

Hemp. — Hemp  is  the  fibrous  portion  of  the  bark  of  an  an- 
nual plant,  ( Cannabis  sativa)  and  is  of  great  use  in  the  manu- 
facture of  cordage  and  canvass.  The  fibres  are  separated  from 
the  rest  of  the  stalks,  by  the  decomposition  of  the  latter.  In 
the  process  of  dew  rotting,  the  hemp  is  exposed  on  the  grass 
for  a  number  of  weeks  to  the  weather.  In  that  of  water  rotting 
it  is  immersed  for  a  part  of  the  time  in  water,  and  subsequently 
exposed  to  the  weather.  By  these  processes,  the  solid  parts  of 
the  hemp  decay ;  whilg  the  flexible  fibres  remain  strong  and  but 
little  impaired.  The  decayed  portion  is  afterwards  broken  up, 
by  the  operations  of  an  instrument  called  a  brake  ;  and  some- 
times by  a  mill  or  stone  roller.    The  chaff  is  separated  from 


MATERIALS  USED   IN  THE  ARTS. 


33 


the  fibres  by  the  strokes  of  a  wooden  scotching,  or  swingling 
knife  ;  and  the  fibres  still  further  cleansed  by  combing  them  on 
an  instrument  called  a  heckle. 

Flax. — Flax  is  also  the  fibrous  bark  of  an  annual  plant, 
(Linum  usitatissimum,)  which  is  smaller  and  finer  than  hemp ; 
and  constitutes  the  material  of  linen  cloth.  Flax  is  rotted,  and 
subsequently  dressed,  much  in  the  same  manner  as  hemp. 
When,  however,  it  is  intended  for  finer  uses,  as  for  cambric, 
lace,  &:c.,  it  is  scraped  with  a  blunt  knife  upon  leather,  and  the 
fibres  separated  and  straightened  with  a  brush.  A  method  has 
been  introduced  in  England,  of  dressing  flax  by  machinery,  in 
its  recent  state,  without  rotting.  This  method  is  represented 
as  highly  economical,  affording  more  flax,  and  of  a  stronger 
texture,  than  that  produced  in  the  common  way.  ^  The  fibres 
of  flax  and  hemp  are  long,  straight,  and  unyielding,  so  that 
they  cannot  be  spun  by  the  same  machinery  which  is  used 
for  cotton  and  wool. 

Cotton. — Cotton  is  the  product  of  the  Gossypium  herbaceum, 
an  Oriental  plant,  now  cultivated  in  most  parts  of  the  world, 
which  possess  a  sufficiently  warm  climate.  It  grows  in  pods, 
forming  a  light,  woolly  investment  to  the  seeds ;  and  seems  in- 
tended by  nature  to  assist  in  their  dispersion  by  the  winds. 
The  fibres  of  cotton  are  extremely  fine,  delicate,  and  flexile. 
When  examined  by  the  microscope,  they  are  found  somewhat 
flat,  and  two  edged  or  triangular.  Their  direction  is  not  straight, 
but  contorted  ;  so  that  the  locks  can  be  extended  or  drawn  out 
without  doing  violence  to  the  fibres.  These  properties  render 
cotton  peculiarly  adapted  for  the  operations  of  machinery,  and 
have  given  employment  to  a  vast  amount  of  manufacturing  skill 
and  industry,  both  in  Great  Britain  and  this  country. 

Cotton,  after  being  gathered,  is  cleansed  from  the  seeds  by 
a  machine  called  a  gin,  of  which  there  are  two  kinds.  The 
roller  gin  consists  essentially  of  two  small  cylinders  revolving 
in  contact,  or  nearly  so,  with  each  other.    The  cotton  is  drawn 

*  See  Brande's  quarterly  Journal,  vol.  iv.  p.  329. 
5 


34 


MATERIALS  USED   IN  THE  ARTS. 


between  these  rollers,  while  the  seeds,  being  too  large  to  pass, 
are  left  behind,  and  fall  out  on  one  side.  The  saw  gin,  invent- 
ed by  Mr  Whitney,  is  intended  for  those  sorts  of  cotton,  the 
seeds  of  which  adhere  too  strongly  to  be  separated  by  the 
former  method.  It  consists  of  a  receiver,  having  one  side  cov- 
ered with  strong  parallel  wires,  placed  like  those  of  a  cage,  and 
about  an  eighth  of  an  inch  apart.  Between  these  wires  enter 
an  equal  number  of  circular  saws,  revolving  on  a  common  axis. 
The  teeth  of  these  saws  entangle  the  cotton  and  draw  it  out 
through  the  grating  of  wires,  while  the  seeds  are  prevented  by 
their  size  from  passing.  The  cotton  thus  extricated  is  swept 
off  from  the  teeth  of  the  saws  by  a  revolving  cylindrical  brush ; 
and  the  seeds  fall  out  at  the  bottom  of  the  receiver. 

Turpentine. — Turpentine  is  the  juice  which  exudes  from 
pine  trees.  The  Southern  pitch  pine  furnishes  most  of  that 
used  in  commerce.  It  is  procured  by  making  incisions,  or  cav-  ^ 
ities,  in  the  trunk,  and  dipping  out  the  turpentine  which  col- 
lects. Tar  is  an  impure  turpentine  obtained  by  burning.  The 
resinous  parts  of  the  wood  called  Ughtivood,  are  collected  in 
pits,  and  being  set  on  fire  at  the  top,  a  part  of  the  turpentine  is 
burnt,  while  the  rest  is  melted  and  flows  out  at  the  bottom. 
Pitch  is  tar  inspissated  by  boiling,  or  burning.  If  turpentine  be 
distilled,  the  volatile  portion,  which  passes  over,  is  the  oil  or 
spirit  of  turpentine,  while  the  solid  part  left  behind  is  rosin. 

Caoutchouc. — This  substance,  called  also  elastic  gum  and  In- 
dia rubber,  is  obtained  from  different  vegetables,  but  chiefly 
from  the  Jatropha  elastica.  It  exists  in  the  form  of  juice,  and 
is  dried  by  applying  it,  in  successive  coatings,  to  clay  moulds  of 
various  shapes.  After  it  is  dry,  the  clay  is  crushed  and  shaken 
out.  This  substance  is  wonderfully  flexible  and  elastic,  and 
restores  itself  instantly,  after  being  extended  to  many  times  its 
original  dimensions.  It  is  inflammable  and  used  by  the  inhabi- 
tants of  Cayenne  for  lights.  It  is  insoluble  in  water,  and  in  al- 
cohol ;  but  dissolves  in  ether,  and  in  oils.  These  solutions  have 
been  used  for  varnishes,  but  have  the  disadvantage  that  they  do 
not  readily  dry.    A  mixture  of  oil  of  turpentine  and  alco- 


MATERIALS  USED  IN  THE  ARTS. 


35 


hoi,  *  is  a  solvent  which  has  the  property  of  drying  more  readi- 
ly and  restoring  the  elastic  properties  of  the  gum.  The  crude 
juice  may  also  be  imported,  and  manufactured  into  articles  here,  f 
Slips  of  India  rubber  may  be  made  to  cohere  by  boiling  them 
in  contact  for  a  certain  time  in  water,  and  in  this  way  some  ar- 
ticles are  made.  Caoutchouc  is  of  great  use  in  the  formation 
of  many  instruments,  which  require  to  be  elastic,  and  impene- 
trable to  water.  Shoes  are  now  made  of  it  in  great  numbers, 
and  are  found  to  exclude  perfectly  the  wet.  The  solution  of 
this  gum  spread  upon  leather  and  cloth,  renders  them  water- 
proof, and  even  air-tight.  Its  adhesiveness  and  friction  are  the 
properties  by  which  it  erases  black  lead  from  paper. 

Oils. — Oil  is  an  inflammable  liquid,  which  does  not  unhe 
with  water.  T^olatile  oils  are  those  which  evaporate,  or  may 
be  distilled  without  change,  by  a  moderate  heat.  Of  these, 
the  oil  of  turpentine  is  an  example.  They  are  used  in  the 
arts  for  solvents,  and  in  varnishes.  Fixed  oils  are  those  which 
do  not  evaporate  without  decomposition,  or  chemical  change. 
They  produce  an  unctuous  stain,  which  is  not  discharged  by 
heat.  They  do  not  boil  at  a  temperature  much  short  of  that 
of  melting  lead.  They  unite  with  alkalies,  forming  soaps. 
Some  of  them  are  called /a^  oils,  which  do  not  lose  their  unc- 
tuous character  on  exposure  to  the  atmosphere,  but  assume  a 
state  like  that  of  tallow ;  such  for  example  as  OHve  oil.  Oth- 

*  Chaptal.    Chimin  appl.  aux  Arts. 

+  Mr  Faraday  states  that  the  liquid  caoutchouc,  or  juice,  as  it  came  from  the 
south  of  Mexico,  was  a  pale,  yellow,  thick,  creamy  looking  substance,  of  a  uni- 
form consistency,  with  a  disagreeable  acescent  odor.  When  exposed  to  the 
air  in  films,  it  is  soon  dried,  leaving  caoutchouc  of  the  usual  appearance  and 
color.  One  hundred  parts  of  the  sap  left  nearly  fortyfive  of  solid  matter. 
Heat  caused  an  immediate  coagulation  of  the  sap,  the  caoutchouc  separating 
in  a  solid  form.  When  the  sap  is  purified  by  repcuted  washings  with  water, 
the  caoutchouc  rises  each  time  to  the  surface,  it  is  obtained  of  a  white  color, 
and  afterwards,  when  perfectly  dry,  it  becomes  transparent,  colorless,  and  elas. 
tic.  A  solution  of  caoutchouc  in  oil  was  obtained  by  mixing  the  juice  with 
olive  oil  and  heating  the  mixture  so  as  to  drive  off  the  aqueous  parts.  This 
promises  to  be  a  useful  element  in  varnishes.  See  Brande's  Journal,  No.  xli. 
page  19. 


36 


MATERIALS  USED  IN  THE  ARTS. 


ers  are  called  drying  oils,  which  become  solid  in  llic  air,  after 
exposure  for  a  certain  time,  and  remain  transparent.  This  is 
the  case  with  linseed  oil.  Fat  oils  are  used  in  the  arts,  to  give 
flexibility  to  other  materials ;  to  diminish  their  friction,  and  to 
protect  them  from  water.  Drying  oils  are  largely  consumed  as 
ingredients  in  paints,  printers'  ink,  and  varnishes. 

Resins. — ^Various  resinous  substances  are  employed  in  the 
arts.  They  are  fusible,  inflammable,  soluble  in  oil  and  alcohol ; 
but  insoluble  in  water.  For  ordinary  purposes  the  rosin  of  the 
pine  is  employed,  being  the  cheapest.  For  varnishes,  copal, 
mastic,  anime,  and  some  others  are  used.  The  basis  of  sealing 
wax  is  the  resin  called  lac,  which  is  deposited  on  trees  in  In- 
dia by  an  insect. 

Starch. — Starch  or  Fecula,  is  a  white  substance,  obtained 
from  farinaceous  grains  and  roots.  It  is  insoluble  in  cold  wa- 
ter, but  dissolves  readily  in  hot  water.  In  alcohol  it  does  not 
dissolve.  In  Europe  starch  is  commonly  made  from  wheat. 
In  this  country  it  is  prepared,  for  manufacturing  purposes,  from 
potatoes.  For  this  purpose  the  potatoes  are  rasped,  or  ground 
up,  by  a  machine,  to  a  pulp.  This  pulp,  when  washed  with 
cold  water,  yields  a  white  powder,  which,  on  subsiding,  proves 
to  be  pure  starch.  It  is  heavier  and  goes  further,  for  practical 
purposes,  than  the  starch  of  wheat.  Starch  is  largely  consum- 
ed in  cotton  factories  in  the  process  of  dressing,  he. 

Gum. — The  true  gums  are  those  which  dissolve  in  water, 
either  hot  or  cold,  and  form  with  it  a  thick,  mucilaginous  solu- 
tion. They  do  not  dissolve  in  alcohol,  nor  melt  by  heat.  The 
species  principally  used  are  the  gum  arahic,  gum  tragacanth, 
and  gum  Senegal.  Gum,  in  the  state  of  mucilage,  is  employed 
to  give  firmness  and  lustre  to  linen.  Calico  printers  use  it  in 
great  quantities,  to  give  their  colors  such  a  degree  of  consisten- 
cy, as  will  prevent  them  from  running  upon  the  cloth.  It  is 
made  to  form  an  ingredient  in  writing  ink,  and  in  water  colors, 
for  the  same  reason. 


MATERIALS   USED   IN   THE  ART3. 


37 


MATERIALS  FROM  THE  ANIMAL  KINGDOM. 

Skins. — The  cutis,  or  true  skin  of  animals,  from  which 
leather  is  made,  is  composed  of  fibres  irregularly  situated,  and 
closely  interwoven.  They  are  capable  of  being  dissolved  by 
long  boiling  in  water,  and  are  found  to  consist  almost  wholly  of 
gelatin,  or  glue.  The  skins  of  a  great  variety  of  animals  are 
used  in  the  manufacture  of  leather.  It  has  been  found  that 
those  skins  which  are  most  flexible,  and  most  easily  dissolved, 
afford  the  poorest  leather  and  the  weakest  glue  ;  while  those 
which  are  tough,  and  difficult  of  solution,  yield  leather  and 
glue  of  the  best  quality. 

Hair  and  Fur. — The  hairs  of  animals  consist  of  slender, 
flexible  tubes,  having  a  consistence  like  that  of  horn,  and  pos- 
sessing the  chemical  properties  of  coagulated  albumen.  The 
surface  of  hairs  are  covered  with  minute  scales  or  asperities, 
which  give  them  a  rough  feel  when  they  are  rubbed  upward  ; 
and  which  cause  them  to  entangle  each  other  in  the  processes 
of  felting  and  fulling.  Fur  consists  of  very  fine  hair,  thickly 
set,  and  commonly  contorted.  It  is  a  very  slow  conductor  of 
heat,  and  is  provided  by  nature  for  the  clothing  of  animals  in 
high  latitudes.  Hair  is  a  durable  and  very  elastic  substance, 
and  is  converted  to  many  useful  purposes.  By  means  of  a  lin- 
en warp,  it  is  woven  into  cloth  for  furniture.  It  forms  the  most 
elastic  stuffing  for  cushions  and  mattresses.  It  is  combined 
with  mortar  in  plastering,  to  increase  its  cohesiveness.  Furs 
are  converted  to  important  uses,  in  clothing  and  in  felting. 

Q^nills  and  Feathers. — The  structure  of  the  quills  and  feath- 
ers of  birds  is  remarkably  fitted  to  combine  strength  and  elasti- 
city with  Hghtness  ;  the  mechanism  of  the  tube,  shaft,  and 
feathering,  being  all  adapted  to  this  purpose.  *  The  tube,  or 
barrel  of  a  quill,  consists  of  two  laminae  or  layers,  the  outer- 
most of  which  has  transverse  fibres,  and  the  inner,  longitudinal. 
It  is  the  first  of  these  which  is  scraped  off  to  prepare  the  quill 

'  *  Sec  Chapter  II. 


38 


MATERIALS  USED  IN  THE  ARTS. 


for  splitting.  Quills  are  rendered  transparent  by  exposing 
thenn  to  heat  and  moisture.  The  process  recommended  by 
M.  Schloz,  is  to  expose  the  quills  to  hot  steam,  by  suspend- 
ing them  in  a  covered  vessel  which  contains  water  in  the  bot- 
tom, and  is  kept  boiling  for  four  hours,  the  quills  being  immers- 
ed in  the  vapor  only.  At  the  end  of  this  time  they  are  with- 
drawn, and  the  next  day  cut,  wiped,  and  dried  with  a  moderate 
heat.  Feathers^  as  they  are  obtained  from  common  birds,  and 
down,  which  is  procured  from  the  aquatic  birds  of  northern 
climates,  are  among  the  most  elastic  substances  known,  and  also 
the  slowest  conductors  of  heat.  These  properties  are  the 
foundation  of  their  usefulness.  The  chemical  composition  of 
feathers  is  nearly  similar  to  that  of  hair.  * 

Wool. — Wool  is  a  fine,  soft,  long,  and  contorted  hair,  deriv- 
ed chiefly  from  the  sheep.  It  is  said  to  be  the  result  of  culti- 
vation, and  not  to  be  found  in  the  wild  sheep,  which  is  covered 
with  short  hair.  Removal  to  a  tropical  climate  causes  the  fleeces 
of  sheep  to  fall  off,  and  to  be  succeeded  by  a  covering  of  short 
hair.  Wool  is  an  invaluable  material  in  the  clothing  of  civiliz- 
ed nations.  The  fineness  and  position  of  its  fibres  enables  it  to 
be  drawn  out  like  cotton,  and  to  be  spun  by  machinery.  Their 
roughness  and  tendency  to  curl,  causes  the  fibres  to  be  consoli- 
dated in  the  process  of  felting. 

Silk. — Silk  is  spun  by  the  larvse  or  caterpillars  belonging  to 
different  species  of  Phalcena.  It  forms  the  ball  or  cocoon  in 
w^hich  the  silk  worm  envelopes  himself  in  passing  to  the  chrysalis 
state.  The  fibre,  which  constitutes  this  ball,  is  so  small,  that  a 
single  thread,  when  unwound,  is  often  twelve  hundred  yards  in 
length.  The  original  threads  are  too  fine  for  manufacturing 
purposes,  and  therefore  in  winding  or  reeling  them  off*  from  the 
cocoons,  the  ends  or  threads  of  several  cocoons  are  joined  to- 
gether, and  reeled  out  of  warm  water,  which  softens  their  nat- 
ural gummy  covering,  and  causes  them  to  cohere  into  a  single 

*  Feathers  are  purified  by  exposing  them  to  heat ;  also  by  immersing  them 
in  Ume  water  for  several  days,  and  afterwards  washing  them  with  pure  water, 
and  drying.    This  process  extracts  the  animal  oil. 


MATERIALS  USED  IN  THE  ARTS.  39 

thread.  Silk,  as  it  is  spun  by  the  animal,  is  of  a  color  varying 
from  white  to  reddish  yellow.  Its  texture  is  very  strong  and 
elastic.  It  communicates  to  water  a  mucilaginous  character, 
owing  to  the  solution  of  its  gummy  part ;  but  the  silk  itself  is 
insoluble  in  water  or  alcohol. 

Bone  and  Ivory. — The  bones  of  animals  are  composed  of  a 
white,  hard,  lamellar  substance,  consisting  chiefly  of  phosphate 
of  lime,  with  a  small  portion  of  other  earths,  and  impregnated 
with  oily  and  gelatinous  matter.  Exposure  to  heat  causes  them 
to  soften  and  crumble.  Bone  is  used  in  the  arts  for  the  han- 
dles of  cutlery,  and  various  articles  of  turners'  work.  It  is 
whitened  by  exposure  to  the  sun  and  weather,  and  sometimes 
by  the  use  of  chlorine  gas.  It  is  wrought  by  sawing,  turning, 
he,  and  polished  with  pumice  and  tripoli.  Ivory  is  the  mate- 
rial of  the  elephant's  tusks.  It  agrees  with  bone  in  its  principal 
properties,  bat  is  more  compact,  hard,  and  white,  and  receives 
a  finer  polish.  When  burnt  in  close  vessels  and  afterwards  re- 
duced to  powder,  it  furnishes  the  pigment  called  ivory  black. 
The  shells  of  marine  animals,  differ  from  bone  in  being  compo- 
sed of  carbonate,  instead  of  phosphate  of  lime. 

Horn. — Horn  differs  from  bone,  not  only  in  its  texture, 
which  is  softer,  but  also  in  its  composition,  being  composed 
chiefly  of  animal  matter  resembling  coagulated  albumen,  and 
containing  but  little  lime.  Horn  when  heated  becomes  soft, 
flexible,  and  plastic,  capable  of  being  cemented  and  pressed  by 
moulds  into  a  great  variety  of  shapes. 

Tortoise  Shell. — This  substance  exists  in  the  form  of  plates 
on  the  outside  of  the  shell  of  a  species  of  sea  turtle  ( Testu- 
do  imbricata).  It  resembles  horn  in  its  general  properties,  and 
like  that  article  may  be  wrought  by  softening  it  in  boiling  water, 
and  subjecting  it,  while  hot,  to  pressure  in  moulds.  The  edges 
of  different  pieces,  by  pressing  them  with  heated  irons,  may  be 
joined  together  and  made  to  cohere  firmly. 

Whalebone. — This  substance  is  obtained  from  the  mouth  of 
several  species  of  whale,  where  it  exists  in  the  form  of  plates 
arranged  on  the  outer  edge  of  the  upper  jaw.    These  plates 


40 


MAtERlALS  Ui^ED  1J<  THE  ARTS. 


terminate  in  a  kind  of  hair.  Whalebone,  in  its  texture  and 
chemical  properties,  is  very  similar  to  horn.  It  is  strong,  light, 
and  elastic,  on  which  accounts  it  is  applied  to  various  mechani- 
cal uses.  Whalebone,  when  heated  by  steam,  or  boiling  water, 
becomes  more  flexible,  and  if  bent  into  any  shape,  retains  its 
form  on  cooling.  Hence  it  has  been  manufactured  into  various 
woven  fabrics.  *  It  may  be  cemented  in  the  same  way  as  horn 
or  turtle  shell. 

Glue. — The  skins,  tendons,  membranes,  &z;c.  of  animals,  are 
composed  principally  of  a  substance  known  in  chemistry  by  the 
name  of  gelatin.  •  This  substance  is  not  soluble  in  cold  water, 
but  dissolves  freely  in  boiling  w^ater,  and  on  cooling  assumes  the 
state  of  jelly.  It  has  great  affinity  for  tannin^  which  exists  in 
astringent  barks  ;  and  on  this  affinity  depends  the  manufacture 
of  leather.  Common  glue  is  impure  gelatin,  obtained  from 
hoofs,  ears,  and  refuse  portions  of  hides.  These  are  first 
cleansed,  then  boiled  to  a  jelly,  which,  on  cooling,  is  cut  into 
squares  and  dried  upon  nets.  Size  is  a  finer  kind  of  glue, 
made  with  more  care,  from  select  materials.  Isinglass  is  a  still 
more  delicate  sort,  prepared  from  the  swimming  bladders  of 
fish.  Glue  is  a  cementing  material  of  unequalled  strength,  for 
wood  and  fibrous  substances.  It  is  employed  in  different  states 
of  purity,  by  carpenters,  hatters,  paper  makers,  linen  manufac- 
turers, gilders,  painters  in  distemper,  and  refiners  of  liquors. 
In  the  state  of  a  stiff  jelly,  it  forms,  with  treacle,  the  elastic  cylin- 
ders, used  to  distribute  and  apply  the  ink,  in  printing. 

Oil. — The  oil  of  animals  belongs  to  the  class  of  fixed  and 
fat  oils.  The  oil  of  those  animals  which  live  in  a  cold  medium, 
as  whales,  remains  fluid  at  common  temperatures  ;  but  that  of 
most  land  animals,  becomes  solid,  when  cooled  below^  the  heat 
of  the  living  body.  Tallow,  the  hardest  kind,  is  obtained  from 
ruminating  quadrupeds.  Animal  oils  are  appropriated  to  the 
same  purposes  as  the  vegetable  ;  but  tlieir  great  use  is  to  fur- 
nish light,  by  their  combustion. 


*  Repertory  of  Arts,  1807,  page  411. 


MATERIALS  USED  IN  THE  ARTS. 


41 


Wax. — Wax,  in  its  crude  state,  is  obtained  by  melting  the 
honeycomb  of  the  bee.  It  is  commonly  classed  with  vegetable 
substances,  but  the  experiments  of  Huber  have  shown,  that 
it  is  produced  by  the  bees  themselves,  and  not  gathered  by 
them  directly  from  plants,  as  was  formerly  supposed.  Wax 
melts  with  a  gentle  heat,  at  one  hundred  and  fortytwo  degrees 
of  Fahrenheit,  is  inflammable,  dissolves  in  boiling  alcohol,  ether, 
and  fixed  oils ;  but  is  insoluble  in  water.  Beeswax  is  de- 
prived of  its  coloring  matter  by  bleaching.  To  effect  this, 
the  melted  wax  is  suffered  to  run  through  holes  in  the  bottom 
of  a  vessel,  upon  the  surface  of  a  cylinder  which  is  kept  revolv- 
ing in  water,  by  which  means  the  wax  is  spread  out,  and  cooled  in 
the  form  of  thin  laminae  or  ribbands.  It  is  then  exposed  to  the 
light  and  air  upon  frames,  and  occasionally  wet,  till  the  bleach- 
ing is  completed.  Bayberry  or  myrtle  wax  is  a  harder  sub- 
stance than  beeswax,  obtained  from  the  berries  of  the  myrica 
cerifera,  by  boiling  them  in  water. 

Phosphorus. — Phosphorus  is  a  simple,  combustible  body, 
usually  obtained  from  animal  bones.  It  is  of  a  soft,  waxy  con- 
sistence, and  is  luminous  in  the  atmosphere  at  common  tempera- 
tures. At  one  hundred  and  fortyeight  degrees  of  Fahrenheit, 
it  takes  fire  and  burns  with  great  brilliancy.  On  this  account 
it  should  be  kept  in  water.  Phosphorus  is  the  agent  in  some 
kinds  of  apparatus  for  procuring  fire. 

References.  Among  the  works,  which  may  be  usefully  consulted 
on  the  subjects  of  this  chapter,  are  Cleveland's  Mineralogy,  2  vols. 
8vo.  1822; — Brard,  Mineralogie  appliquee  aux  Ms,  3  torn.  8vo.  Paris, 
1821 ;— Evelyn's  Silva,  2  vols.  4to.  edit,  of  1812  ;— Michaux,  North 
American  Sylva,  3  vols.  8vo.  1817;— Tredgold's  Elementary  Princi- 
ples of  Carpentry,  4to.  1820 ;— Thomson's  Chemistry  ;—Ure's  Dic- 
tionary ; — ViCAT,  Recherches  sur  les  Chaux,  ^c. 


6 


CHAPTER  11. 


OF  THE  FORM,  CONDITION,  AND  STRENGTH  OF  MATERIALS. 

When  materials  are  employed  for  mechanical  purposes,  the 
power  or  strength  with  which  they  resist  external  force,  depends 
not  merely  upon  the  nature  of  the  material,  but  upon  its  shape, 
its  bearings,  and  upon  the  manner  in  which  force  is  applied  to 
it.  It  is,  therefore,  important  to  consider  not  only  the  qualities 
of  individual  substances,  but  Hkewise  the  laws,  which  are  com- 
mon to  different  materials,  by  which  they  act  in  resisting  me- 
chanical change,  from  forces  applied  to  them. 

Modes  of  estimation. — Two  methods  are  employed  in  esti- 
mating the  strength  of  materials,  in  different  forms  and  situa- 
tions ;  one  by  mathematical  computation,  the  other  by  actual 
experiment.  The  first  supposes  the  structure  of  given  bodies 
to  be  homogeneous,  so  that  the  cohesion  of  their  particles  shall 
be  equal  throughout.  In  the  second,  a  single  specimen  is  tak- 
en as  the  representative  of  a  class  ;  or  at  most  the  average  of 
a  number  of  specimens,  is  so  taken.  Neither  method,  there- 
fore, is  to  be  looked  upon  as  precisely  accurate  in  its  results  ; 
yet  these  results  furnish  approximations  to  truth,  which,  in 
many  cases  it  is  useful  to  understand. 

Stress  and  strain. — Professor  Robison,  and  some  other  wri- 
ters on  the  strength  of  materials,  have  enumerated  four  modes, 
commonly  called  strains,  by  which  any  force  or  stress  acting 
upon  a  solid  body  may  operate  to  overcome  the  cohesion  of  its 
particles.  These  are,  1.  By  extension,  producing  a  tendency 
to  rupture ;  as  in  the  case  of  ropes,  tie-beams,  king-posts,  &tc. 
2.  By  compression,  tending  to  shorten  or  crush  the  material ; 
as  in  columns,  walls,  and  foundations.  3.  By  transverse  strain, 
tending  to  produce  flexure  or  fracture  ;  as  in  beams,  rails,  and 


THE  FORM  AND   STRENGTH   OF   MATERIALS.  43 

oars.  4.  By  torsion  or  twisting;  as  in  screws,  rudders,  and 
axles  fixed  to  wheels.  To  these  Dr  Young  has  added  another, 
viz ; — detrusion,  or  pushing  aside,  as  in  the  case  of  a  pin  op- 
erated on  by  the  blades  of  scissors.  The  changes  called  flex- 
ure, or  bending  ;  fracture,  or  solution  of  continuity  ;  and  altera- 
tion, or  permanent  change  of  form  without  separation  ;  are  to 
be  included  in  the  effects  of  force  exerted  on  materials. 

Resistance. — To  these  disturbing  influences,  bodies  oppose 
certain  qualities,  which  depend,  in  part,  upon  the  nature  of  the 
material,  and  in  part  on  its  form,  condition,  and  connexion. 
These  are  their  strength,  by  which  they  resist  all  permanent 
changes  resulting  from  mechanical  force,  but  more  particularly 
fracture.  Their  hardness,  by  which  they  resist  impressions,  or 
superficial  changes.  Their  stiffness,  by  which  they  resist  flex- 
ure or  bending.  Their  elasticity,  by  which  they  regain  their 
original  size  and  form,  after  any  force  producing  mechanical 
change  in  them,  has  ceased  to  operate.  Their  tenacity,  by 
which  they  undergo  permanent  alteration  without  fracture. 
This  quality  is  called  ductility,  when  exposed  to  extension,  and 
malleability,  when  exposed  to  compression.  Some  authors  add 
the  term  resilience,  to  express  the  quality  by  which  a  body  re- 
sists impulse,  like  that  of  a  blow,  in  contradistinction  from 
strength,  by  which  it  resists  pressure. 

Extension. — When  a  bar  of  any  material  is  drawn  in  the 
direction  of  its  length,  its  resistance,  or  strength,  will  be  pro- 
portionate to  its  size  at  the  weakest  point ;  i.  e.  to  the  area  of 
its  cross  section  at  that  point.  The  tie-beam  of  a  roof,  the 
posts  of  a  printing  press,  and  the  shaft  or  piston  rod  of  a  pump, 
are  exposed  to  this  kind  of  strain ;  and  their  weakest  point  is 
commonly  found  at  the  place  where  they  are  perforated,  or 
mortised,  to  connect  them  with  the  other  parts.  Various  ex- 
periments have  been  made  to  determine  the  comparative  strength 
with  which  different  substances  resist  tension.  Although  they 
do  not  fully  agree  in  their  results,  they  nevertheless,  when  taken 
collectively,  afford  approximations  of  some  use  for  practical  pur- 
poses.   An  idea  of  the  relative  strength  of  the  metals,  when  ex- 


44 


THE  FORM,  CONDITION,  AND 


tended,  may  be  obtained  from  Mr  Rennie's  experiments  detailed 
in  the  Philosophical  Transactions  for  1818.  His  experiments 
were  made  with  bars  six  inches  long,  and  a  quarter  of  an  inch 
square.  The  average  number  of  pounds  avoirdupois,  which 
they  supported  respectively,  is,  in  round  numbers,  bs  follows. 
Steel,  about  8000  pounds.  Hammered  iron,  about  4000. 
Gun  metal  and  wrought  copper,  2000.  Cast  copper  and  brass, 
1000.  Tin,  300.  Lead,  100.  Experiments  have  been  made 
on  the  longitudinal  strength  of  the  wood  of  different  European 
trees,  and  similar  experiments,  sufficiently  varied,  on  the  trees 
of  this  continent,  might  be  a  valuable  addition  to  our  knowledge. 

Compression. — When  a  bar  or  beam  is  compressed  in  the 
direction  of  its  length,  it  resists  more  powerfully  than  in  any 
other  way.  ^  If  the  beam  be  long,  and  its  strength  be  overpow- 
ered by  pressure,  it  bends,  and  then  breaks  ;  but  if  its  thickness 
be  as  much  as  a  seventh  part  of  its  length,  it  commonly  swells  in 
the  middle,  splits  and  is  crushed.  When  a  stone  block  or  pillar  is 
crushed,  the  parts  nearest  to  the  force,  break  away  and  slide  off 
diagonally  at  the  sides,  leaving  a  pyramidal  base.  The  lower 
stories  of  buildings,  the  piers  and  piles  of  bridges,  the  spokes 
of  carriage  wheels,  and  the  legs  of  furniture,  are  subjects  of 
this  force.  According  to  Mr  Tredgold,  f  a  cubic  inch  of  mal- 
leable iron  will  support,  without  alteration,  a  weight  of  about 
17000  pounds  ;  cast  iron,  15000  ;  brass,  7000;  oak  and  ma- 
hogany, nearly  4000  ;  tin,  3000 ;  lead,  1500.  Granite  is  crush- 
ed by  11000  pounds  to  the  square  inch;  white  marble,  by 
6000  ;  Portland  stone,  by  4000. 

When  a  force  acts  on  a  straight  column  in  the  direction  of 
its  axis,  it  can  only  extend,  or  compress  it  equally  through  its 
whole  substance.  But  if  the  direction  of  the  force  is  not  in  the 
axis,  but  parallel  to  it,  the  extension  or  compression  will  then 
be  partial.    In  a  rectangular  column  or  block,  when  the  com- 

*  Modulus  of  elasticity. — This  term  has  been  introduced  as  a  measure  to 
express  the  elastic  force  of  any  substance.  The  Modulus  of  el'-isticity  of  a 
substance  is  a  column  of  the  same  substance,  capable  of  producing  a  pressure 
on  its  base,  which  is  to  the  weight  causing  a  certain  degree  of  compression, 
as  the  length  of  the  substance  is  to  the  diminution  of  its  lengtli. 

t  Essay  on  Cast  Iron,  p.  269,  etc. 


STRENGTH  OF  MATERIALS. 


45 


pressing  force  is  applied  to  a  point  more  distant  from  the  axis 
than  one  sixth  of  the  depth,  the  remoter  surface  will  be  no 
longer  compressed,  but  extended.    In  this  case  the  distance 
from  the  axis  of  the  neutral  point,  or  that  which  is  neither  com- 
pressed nor  extended,  will  be  inversely  as  that  of  the  point  to 
which  the  force  is  applied.    For  example,  a  C^A. 
weight  or  compressing  force  being  applied  on  j^^^^^BJ 
one  side  of  the  block  or  column  C  D  E  F,  and  ^^^^^m 
acting  in  a  direction  parallel  to  its  axis,  the  ^^^^^m 
compression  will  extend  only  to  the  hne  A  B,  m 
the  parts  beyond  this  being  extended.  a>     b  ^ 

Lateral  strain. — ^When  a  beam  is  acted  on  transversely,  or 
by  a  lateral  force,  the  effect  produced  is  the  joint  result  of  ex- 
tension and  compression.  For  if  it  be  moved  or  bent  by  such 
a  force,  from  its  original  direction,  the  part  which  becomes  con- 
vex is  extended,  while  the  part  rendered  concave  is  compres- 
sed. The  properties  by  which  a  beam  resists  lateral  pressure,, 
are  its  stiffness  and  its  strength. 

Stiffness. — The  stiffness  of  any  substance  is  measured  by 
the  force  required  to  cause  it  to  bend  or  recede  through  a  given 
small  space  in  the  direction  of  the  force.  It  appears  to  be  gov- 
erned by  different  laws  from  those  of  the  strength  which  resists 
fracture.  When  a  force  is  applied  to  a  beam  transversely,  its 
stiffness  is  directly  as  the  breadth,  and  the  cube  of  the  depth  of 
the  beam,  and  inversely  as  the  cube  of  its  length.  Thus  if 
we  have  a  beam  which  is  twice  as  long  as  another,  we  must 
make  it,  in  order  to  obtain  an  equal  stiffness,  either  twice  as 
deep,  or  eight  times  as  broad.  When  a  beam  is  supported  at 
both  ends,  its  stiffness  is  twice  as  great  as  that  of  a  beam  of  half 
the  length  inserted  in  a  wall,  or  otherwise  firmly  fixed,  at  one 
end.  If  both  ends  are  firmly  fixed,  the  stiffness  is  quadru- 
pled, f 

*  Gregory's  Mathematics  for  practical  men,  389,  also  Young's  Nat.  Philoso- 
phy, i.  139,  and  Tredgold's  Elements  of  Carpentry,  31. 

t  The  quantity  of  timber  being  the  same,  a  beam  will  be  stronger  in  propor- 
tion as  the  depth  is  greater,  but  there  is  a  certain  proportion  between  the  depth 


46 


THE  FORM,   CONDITION,  AND 


Tubes. — A  tube  or  hollow  beam  is  much  stifFer  than  the  same 
quantity  of  matter  in  a  solid  form.  The  stiffness  is  indeed  in- 
creased nearly  in  proportion  to  the  square  of  the  diameter;  since 
the  cohesion  or  repulsion  are  equally  exerted,  with  a  smaller  cur- 
vature ;  and  act  also  on  a  longer  lever.  We  see  this  princi- 
ple applied  in  nature  in  the  stems  of  reeds,  and  the  bones  and 
quills  of  animals. 

Strength. — The  strength  of  beams  of  the  same  kind,  and 
fixed  in  the  same  manner,  in  resisting  a  transverse  force  which 
tends  to  break  them,  is  simply  as  their  breadth,  as  the  square 
of  their  depth,  and  inversely  as  their  length.  Thus  if  a  beam 
be  twice  as  broad  as  another,  it  will  also  be  twice  as  strong,  but 
if  it  be  twice  as  deep,  it  will  be  four  times  as  strong  ;  for  the 
increase  of  depth  not  only  doubles  the  number  of  the  resisting 
particles,  but  also  gives  each  of  them  a  double  power,  by  in- 
creasing the  length  of  the  levers  on  which  they  act.  The  in- 
crease of  the  length  of  a  beam  must  obviously  weaken  it,  by 
giving  a  mechanical  advantage  to  the  power  which  tends  to 
break  it;  and  some  experiments  appear  to  show,  that  the 
strength  is  diminished  in  a  proportion  greater  than  that  in  which 
the  length  is  increased. 

The  strength  of  a  beam  supported  at  both  ends,  like  its  stiff- 
ness, is  twice  as  great  as  that  of  a  single  beam  of  half  the 
length,  which  is  fixed  at  one  end  ;  and  the  strength  of  the  whole 
beam  is  again  doubled,  if  both  the  ends  are  firmly  fixed. 

Place  of  strain. — If  a  weight  or  other  stress  be  placed  on 
any  given  point  of  a  horizontal  bar  which  is  supported  at  both 
ends,  the  strain  on  that  point  will  be  proportional  to  the  rec- 
tangle of  the  two  segments  into  which  the  point  divides  the  bar. 
Hence  the  place  where  the  strain  would  be  greatest  is  in  the 

and  breadth,  which,  if  it  be  exceeded,  the  beam  will  be  liable  to  overturn 
and  break  sideways.  To  avoid  this,  the  breadth  should  never  be  less  than  that 
given  by  the  following  rule,  unless  the  beam  be  held  in  its  position  by  some 
other  means. 

Divide  the  length  in  feet,  by  the  square  root  of  the  depth  in  inches,  and 
^he  quotient  multiplied  by  the  decimal  0.6  will  give  the  least  breadth  that 
should  be  given  to  the  beam.    Tredgold's  Carpentry,  p.  32. 


STRENGTH   OF  MATERIALS. 


47 


middle  of  the  bar,  and  a  given  weight  would  be  most  fikely  to 
break  it  in  that  place. 

Incipient  fracture. — An  incipient  or  partial  fracture,  at  the 
place  of  strain,  weakens  a  beam  more,  than  if  the  whole  side 
of  the  beam  were  cut  away  to  the  same  depth  as  the  fracture. 
This  is  because  the  sound,  or  stronger  parts  of  the  beam  tend 
to  straighten  themselves,  and  thus  increase  the  curvature  at  the 
point  which  is  weakened.  The  same  cause  occasions  the* 
breaking  of  glass  in  the  direction  of  a  cut  made  by  a  diamond^ 
or  of  a  crack  which  has  commenced.  Mr  Emerson  asserts 
that  a  triangular  beam,  which  is  so  strained  that  the  greatest  ex- 
tension takes  place  at  one  of  its  angles,  is  rendered  stronger, 
rather  than  weaker,  by  cutting  away  this  angle  to  a  small  depth, 
so  as  to  convert  the  beam  into  a  four  sided  figure ;  thus  pro- 
ducing the  seeming  paradox  of  a  part  being  stronger  than  the 
whole.  A  sharp  angle  is  indefinitely  weak,  and  fracture  is- 
more  likely  to  begin  in  an  angle,  than  in  a  broad  surface. 

Resilience. — The  action  which  resists  pressure,  is  called 
strength,  and  that  which  resists  impulse,  is  termed  by  Dr  Young, 
resilience.^  The  resilience  is  measured  by  the  product  of 
the  mass,  and  the  square  of  the  velocity  of  a  body  capable  of 
breaking  it,  while  the  strength  is  merely  measured  by  the  great- 
est pressure  that  it  can  support  in  a  state  of  rest. 

The  resilience  of  a  prismatic  beam,  resisting  a  transverse 
impulse,  follows  a  different  law  from  that  which  determines  its 
strength,  for  it  is  simply  in  proportion  to  the  bulk  or  weight  of 
the  beam,  whether  it  be  shorter  or  longer,  narrower  or  wider, 
shallower  or  deeper,  solid  or  hollow.  Thus  a  beam  ten  feet 
long,  will  support  but  half  as  great  a  pressure  without  breaking, 
as  a  beam  of  the  same  breadth  and  depth,  v^^hich  is  only  five 
feet  in  length  ;  but  it  will  bear  the  impulse  of  a  double  weight, 
striking  against  it  with  a  given  velocity,  and  will  require  that  a 
given  body  should  fall  from  a  double  height  in  order  to  break 

it-t 


Nat.  Philosophy,  p.  143—147.       t  Ibid.  p.  148. 


48 


THE  FORM,  CONDITION,  AND 


Shape  of  timber. — It  may  be  inferred  from  the  consideration 
of  the  nature  of  the  different  kinds  of  resistance,  that  if  we 
have  a  cyhndrical  tree  a  foot  in  diameter,  which  is  to  be  form- 
ed into  a  prismatic  beam  by  flattening  its  sides,  we  shall  gain 
the  greatest  stiffness  by  making  the  breadth  or  thickness  six  in- 
ches and  the  depth  ten  and  a  half ;  the  greatest  strength  by  mak- 
ing the  breadth  seven  inches  and  the  depth  nine  and  three 
quarters,  and  the  greatest  resilience  by  making  the  beam 
square-  * 

Torsion. — The  kind  of  strain  called  torsion  or  twisting,  con- 
sists in  the  lateral  displacement  or  detrusion  of  the  opposite 
parts  of  a  sohd,  in  opposite  directions ;  the  central  particles  only 
remaining  in  their  natural  state.  The  strength,  or  rather  stiff- 
ness, with  which  the  shaft  of  a  wheel,  or  crank  resists  torsion, 
increases  in  a  rapid  ratio  to  its  diameter.  Professor  Robison 
has  calculated,  that  the  power  of  resisting  torsion  is  as  the  cube 
of  the  diameter  ;  and  the  more  recent  estimates  of  M.  Duleau 
make  it  as  the  fourth  power  of  the  diameter.  If  the  length 
vary,  the  resistance  to  the  force  of  torsion  will  be  inversely  as 
the  length,  for  obvious  reasons.  It  is  advantageous  in  machin- 
ery to  increase  the  diameter  of  shafts  which  are  exposed  to  this 
strain,  the  amount  of  material  remaining  the  same.  For  this 
purpose  they  are  sometimes  made  hollow,  and  sometimes  wing- 
ed with  lateral  projections. 

Limit  of  hulk. — It  is  important  to  recollect  that  when  the 
bulk  of  a  substance  employed,  becomes  very  considerable,  its 
own  weight  may  bear  so  great  a  proportion  to  its  strength,  as  to 
add  materially  to  the  load  to  be  supported.  In  most  cases,  the 
weight  of  bodies  increases  more  rapidly  than  their  strength,  and 
thus  causes  a  practical  limitation  of  the  magnitude  of  our  ma- 
chines and  edifices.  Thus  a  roof,  or  a  bridge,  may  be  very 
strong,  when  of  small,  or  moderate  size  ;  but  if  the  size  be  ex- 
tended beyond  a  certain  limit,  although  the  materials  and  pro- 
portion of  parts  remain  the  same,  yet  the  structure  will  not  sup- 


*  Young's  Nat.  Philosophy,  p.  149. 


STRENGTH   OF  MATERIALS. 


49 


port  Its  own  weight.  We  see  also  a  similar  limit  in  nature ;  for 
if  trees  and  animals  wer6  made  many  times  larger  than  we  now 
find  them,  and  of  the  same  kinds  of  substance,  they  would  not 
sustain  their  own  weight.  Small  animals  endure  greater  com- 
parative violence,  and  perform  greater  feats  of  strength  in  pro- 
portion to  their  size,  than  large  ones.  It  has  been  observed 
that  whales  are  larger  than  any  land  animals,  because  their  weight 
is  more  equally  supported  by  the  pressure  of  the  medium  in 
which  they  swim. 

Practical  Remarks. — In  frames  of  houses,  and  for  various 
other  purposes,  beams  are  used  of  a  prismatic  form,  having 
straight,  parallel  sides.  But  such  beams,  when  exposed  to  a 
lateral  strain,  are  not  of  equal,  or  duly  proportioned  strength 
throughout ;  and  therefore  a  part  of  them  is  superfluous.  This 
consideration  is  not  of  much  importance  in  ordinary  practical 
cases.  But  in  cases  where  economy  of  the  material  is  impor- 
tant, as  in  cast  iron  railroads,  also  in  machinery  where  it  is  de- 
sirable that  the  moving  parts  should  be  as  light  as  possible,  con- 
sistently with  the  requisite  strength;  it  becomes  of  consequence 
to  ascertain  the  best  form  for  resisting  a  force  with  the  smallest 
amount  of  material.  Mathematicians  have  calculated  the  forms 
of  different  beams,  which  are  suited  to  give  them,  at  all  points, 
a  strength  proportionate  to  the  pressure  they  sustain,  supposing 
the  material  to  be  of  uniform  texture.  But  the  outline  which 
answers  merely  to  mathematical  truth,  is  in  many  cases  too 
scanty  for  actual  employment ;  so  that  in  order  to  obtain  suffi- 
cient length  for  a  secure  connexion  of  the  beam  with  its  bear- 
ings, it  is  necessary  to  include  the  mathematical  figure  in  a  some- 
what similar  one,  of  larger  dimensions.  The  following  rules 
are,  most  of  them,  given  in  substance  by  Mr  Tredgold.  * 

If  a  beam  be  supported  at  both  ends,  and  the  load  applied 
at  some  one  point  between  the  supports,  and  always  acting  in 
the  same  direction,  the  best  plan  appears  to  be,  to  make  the  ex- 
tended side,  or  that  opposite  the  load,  perfectly  straight ;  and 


*  Essay  on  Cast  Iron,  Art.  21.  et  seq. 
7 


50 


THE  FORM,   CONDITION,  AND 


to  make  the  breadth  equal  throughout  the  whole.  Then  the 
mathematical  form  of  the  compressed  side  will  be  that  which  is 
formed  by  drawing  two  semi-parabolas,  A  C  D  and  BCD, 
their  vertices  being  at  A  and  B,  and  C  being  the  point  where 
the  force  acts.  Now  since  the  curve  terminates  at  A,  it  is  ne- 
cessary, in  applying  it  to  use,  to  add  some  such  parts  as  are 
indicated  by  the  hues  extending  to  E  and  F  at  the  extremities, 
for  the  sake  of  better  support. 


The  same  form  is  proper  for  a  beam  supported  in  the  middle, 
as  the  beam  of  a  balance.  If  the  beam  be  strained,  sometimes 
from  one  side  and  sometimes  from  the  other,  as  in  the  beam  of 
a  steam  engine,  then  both  sides  should  be  of  the  same  form, 
and  E  A  and  F  B  should  each  be  equal  to  half  C  D. 


It  is  sometimes'  desirable  to  preserve  the  same  depth  through- 
out; and  in  this  case  the  section  through  the  length  of  the 
beam,  made  perpendicular  to  the  direction  of  the  straining  force, 
should  be  a  rhombus  or  trapezium,  as  in  the  annexed  figure, 
the  force  acting  perpendicularly  at  C,  and  the  points  of  support 
being  at  A  and  B.  To  give  this  figure  stability,  the  ends  may 
be  formed  as  shown  in  the  continued  outline. 


STRENGTH   OF  MATERIALS. 


61 


If  a  beam  be  intended  to  support  a  weight  uniformly  distrib- 
uted throughout  its  length,  or  a  load  rolling  over  it,  as  in  a  rail- 
way, the  line  bounding  the  compressed  side  should  be  a  semi- 
ellipse,  the  other  side  being  straight.  In  practice  the  semi-el- 
lipse may  be  included  in  a  portion  of  a  circle,  to  give  the  re- 
quisite bearings. 

A,B,  ends  of  the  elliptic  curve.  C,D,  endsof  the  circular 
curve. 


Where  it  is  necessary  that  the  upper  side  should  be  straight, 
the  above  form  may  be  inverted,  and  the  ends  adapted  to  the 
bearings. 

Beams  which  are  fixed  at  one  end  only  and  support  weights, 
should  decrease  as  they  recede  from  the  wall,  or  point  of  fix- 
ture. If  the  w^eight  be  at  the  extremity,  the  outline,  in  a  beam 
cut  from  a  vertical  plank,  should  be  parabolic ;  but  if  equally 
distributed  throughout,  it  may  be  straight. 


If  a  beam  be  firmly  fixed  at  both  ends,  and  supports  a  weight 
in  the  middle,  it  should  be  largest  at  the  ends  and  in  the  mid- 
dle, the  outlines  being  parabolic.  In  the  annexed  figure  the 
shaded  part  shows  the  mathematical  form,  and  the  outline  the 
form  for  practical  purposes. 


62 


THE  FORM  AND  STRENGTH  OF  MATERIALS. 


For  resisting  a  cross  strain,  it  is  advantageous  that 
the  edges  of  a  beam  should  be  made  thicker  than  the 
rest  of  its  substance,  so  that  a  section  of  the  beam 
would  be  nearly  such  as  is  seen  in  the  adjoining 
figure.  * 

It  must  be  recollected  that  the  foregoing  rules  prescribe  only 
a  general  form,  the  proportions  of  which  must  vary  with  the 
nature  of  the  material,  and  the  degree  of  resistance,  or  load  to 
be  supported. 


Works  which  treat  of  the  strength  of  materials. — Robison's  Mechani- 
cal Philosophy,  4  vols.  8vo.  1822;  vol.  i.  p.  369,  &c.; — Barlow  on  Tim- 
ber, 8vo.  1823  ;— Young's  Natural  Philosophy,  2  vols.  4to.  1807 ;  vol.  i. 
p.  135,  &.C. ;  vol.  ii.  art.  333,  &.c. ; — Rennie,  in  the  Philosophical  Trans- 
actions, 1818; — DuLEAU,  Annates  de  Chimie,  torn.  xii. ; — Tredgold's 
Elementary  Principles  of  Carpentry,  4to.  1820  ; — Tredgold's  Essay  on 
Cast  Iron,  8vo.  1824; — Emerson's  Mechanics; — Gregory's  Mechan- 
ics, 3  vols.  8vo.  edit.  1826; — Gregory's  Mathematics  for  Practical 
Men,  8vo.  1825. 

*  For  the  form  best  suited  to  resist  longitudinal  pressure,  see  the  article 
Column  in  Chap.  VII. 


CHAPTER  III. 


THE  ARTS  OF  WRITING  AND  PRINTING. 

Letters. — The  arts  of  writing  and  printing,  although  com- 
paratively simple  in  their  processes,  are  superior  to  most  other 
arts  in  the  importance  of  their  consequences.  Before  the  in- 
vention of  letters,  the  growth  of  knowledge  was  opposed  by 
insurmountable  obstacles.  Tradition,  which  was  the  earliest 
mode  of  transmitting  knowledge,  depended  upon  the  memory 
and  the  will  of  individuals,  and  was  of  course  uncertain  of 
continuance.  The  principal  adventitious  aids  brought  to  the 
assistance  of  traditionary  knowledge,  were  the  erecting  of  mon- 
uments, the  celebration  of  periodical  days  or  years,  the  use  of 
poetry,  a  language  more  captivating  and  more  easily  remem- 
bered than  mere  narration  of  facts  ;  and  finally  an  approach 
to  written  characters  in  symbolical  drawings  and  hieroglyphic 
sketches.  All  these  methods,  however,  have  failed  in  the  object 
for  which  they  were  intended.  The  founders  of  the  Pyra- 
mids have  not  been  able  to  convey  to  us  their  names,  and  the 
productions  of  the  earliest  sages  and  poets  can  never  be  appre- 
ciated from  acquaintance.  The  symbolic  sculptures  which 
cover  the  antiquities  of  Egypt,  are  now  subjects  of  empty  spec- 
ulation to  the  curious.  History  must  have  remained  uncertain 
and  fabulous,  and  science  been  left  in  perpetual  infancy,  had  it 
not  been  for  the  invention  of  written  characters. 

Invention  of  Letters. — The  credit  of  the  first  introduction  of 
letters,  was  claimed  by  the  Egyptians  and  Phoenicians,  Jews, 
Chinese,  and  other  nations.  Their  origin  is  extremely  ancient 
and  of  course  preceded  all  authentic  history,  which  was  not 
inspired.  If  we  believe  Pliny,  sixteen  characters  of  the  Gre- 
cian alphabet  were  introduced  by  Cadmus  the  Phoenician,  1500 


64  THE   ARTS   OF  WRITING  AND  PRINTING. 

years  before  Christ.  Four  more  were  added  by  Palamedes 
during  the  Trojan  war,  and  four  afterward  by  Simonides.  It 
is  not  probable,  however,  that  the  Greek  w^as  the  oldest  alpha- 
bet. Mr  Astle  considers  the  Phoenicians  as  having  the  strong- 
est claim  to  be  considered  the  first  inventors  of  letters. 

Arrangement  of  Letters. — The  mode  of  arranging  letters  has 
been  subject  to  considerable  variation,  some  nations  having 
written  in  perpendicular  lines,  others  from  right  to  left,  and  oth- 
ers in  lines  alternately  reversed,  as  in  the  (iii^r^o(pt}^ov  of  the 
ancient  Greeks.  *  The  mode  of  writing  from  left  to  right,  now 
generally  pursued,  is  the  most  natural;  because  the  hand,  as  it 
advances  in  this  direction,  leaves  constantly  uncovered  that  por- 
tion of  the  page,  upon  which  writing  has  been  made. 

Writing  Materials. — The  most  ancient  materials  employed 
for  writing,  appear  to  have  been  the  surfaces  of  stones  and 
bricks.  The  ten  commandments  were  witten  upon  stone,  and 
the  arrow-headed  alphabet,  as  it  is  called,  belonging  to  an  ex- 
tinct language,  is  only  known  to  us  by  the  pages  of  inscriptions 
which  remain  on  the  Babylonian  bricks.  After  these,  plates  of 
metal,  of  various  kinds,  were  employed.  The  Romans  wrote 
upon  tablets  of  brass  thinly  coated  with  wax,  using  an  iron  pen- 
cil with  a  sharp  point  denominated  Stylus.  Lead  was  also  used 
by  them,  and  at  the  siege  of  Modena  a  correspondence  was  car- 
ried on  by  Decimus  Brutus,  and  the  consul  Hirtius,  upon  plates 
of  lead.  Pausanias  mentions  books  of  Hesiod,  and  Pliny  speaks 
of  public  records,  inscribed  on  the  same  material.  A  less  du- 
rable, but  more  cheap  receptacle  for  written  characters,  was 
found  in  the  leaves  of  trees  and  their  inner  bark,  denominated 

*  The  bustrophedon  was  disused  by  the  Greeks  about  450  years  before  the 
christian  era  ;  but  a  similar  method  appears  to  have  been  in  use  among  the  Irish 
at  a  much  later  period.  The  following  example  of  the  Greek  bustrophedon  is 
from  an  inscription  on  a  marble  in  the  national  museum  at  Paris. 

NEKH0E  NEM  20AAT 
API2TOKTAE2  NOH2EN 
em  decalp  sullyH 
Aristocydes  designed  me. 


THE   ARTS   OF   WRITING   AND  PRINTING. 


50 


liher  by  the  Latins.  These  were  used  for  the  more  temporary 
or  perishable  writings.  * 

Papyrus. — As  the  literature  of  antiquity  advanced,  it  became 
necessary  to  find  a  material  adapted  for  works  of  magnitude, 
which,  besides  permanency  and  enlarged  size,  should  have  a 
fineness  of  texture  sufficient  to  permit  a  large  surface  to  be 
folded  into  a  compact  form.  A  species  of  reed,  growing  in 
Egypt,  was  found  capable  of  being  manufactured  into  a  sub- 
stance of  this  sort.  Sheets  and  rolls  were  prepared  from  it  of 
the  finest  texture,  and  of  any  dimensions,  and  it  became  the 
receptacle  on  which  a  great  part  of  the  ancient  manuscripts  were 
written.  This  was  the  celebrated  Egyptian  papyi'us.  The 
discovery  of  its  manufacture,  though  it  afforded  a  substance  far 
inferior  to  modern  paper,  w^as  nevertheless  a  great  auxiliary  to 
ancient  learning,  and  became  the  means  of  a  much  more  exten- 
sive multiplication  of  manuscripts  than  could  have  taken  place 
had  it  remained  unknown.  The  papyrus  was  an  aquatic  reed 
growing  on  the  banks  of  the  Nile,  f  The  manufacture  of  paper- 
was  performed  by  divesting  this  reed  of  its  outer  cover- 
ing and  then  carefully  separating  the  internal  membranes  or 
laminae  by  the  point  of  a  needle  or  knife.  J  These  laminae 
were  spread  parallel  to  each  other  on  a  table,  having  their  edges 
in  contact,  in  sufficient  numbers  to  form  a  sheet.    A  second 

*  Pliny  says  that  tables  of  wood  were  in  use  for  writing  before  the  time  of 
Homer.  In  the  Slonian  library  at  Oxford,  there  are  some  specimens  of  an- 
cient Arabic  writing  on  boards  about  two  feet  long  and  six  inches  wide. 

The  edicts  of  the  Roman  Senate  were  written  on  tablets  of  ivory,  thence 
denominated  libri  elephantini. 

According  to  Pliny,  the  most  ancient  mode  of  writing,  was  upon  the  leaves 
of  Palm  trees,  afterward  upon  the  inner  bark  of  trees.  This  method  is  still 
common  inTanjore,  and  some  other  parts  of  the  East  Indies  where  the  palmy- 
ra leaf  is  used. 

The  old  Egyptians  frequently  wrote  on  linen,  and  specimens  of  this  kind 
are  sometimes  found  inclosed  in  the  garments  or  swathing  clothes  of  mum- 
mies. 

t  Cyperus  papyrus.  L. 

t  The  delicate  substance  now  imported  from  India  under  the  name  of  rice 
paper,  is  a  cellular  membrane  of  the  Artocarpus  incisifolia,  or  Bread-fruit-trec. 
Brewster's  Journal,  iii.  136. 


56 


THE  ARTS   OF   WRITING  AND  PRINTING, 


Stratum  was  then  laid,  with  the  strips  crossing  those  of  the  first 
at  right  angles.  The  whole  was  moistened  wuth  water  and 
subjected  to  pressure  between  two  polished  surfaces.  Upon 
drying,  the  mass  was  found  agglutinated  into  a  smooth  and  uni- 
form sheet.  The  adhesion  of  the  strips  of  papyrus  to  each 
other  was  doubtless  owing  to  the  glutinous  juice  of  the  reed, 
though  the  Romans,  who  were  ignorant  of  the  Egyptian  mode 
of  manufacturing  it,  attributed  this  effect  to  a  peculiar  quality 
in  the  waters  of  the  Nile.  The  most  delicate  paper,  which 
was  made  from  the  inner  membranes  or  tunics  of  the  reed,  was 
rendered  extremely  white,  and  polished  by  rubbing  it  with  a 
shell  or  tooth  of  an  animal. 

Herculaiieum  Manuscripts. — The  papyrus  continued  in  use 
as  late  as  the  tenth  or  twelfth  century,  when  it  was  superseded  by 
parchment  and  cotton  paper.  A  few  ancient  manuscripts  writ- 
ten on  it  are  preserved  as  curiosities  in  different  libraries  of 
Europe,  though  they  are  less  numerous  than  those  of  parchment 
and  vellum'.  The  most  interesting  collection  of  papyri  is  un- 
doubtedly that  found  at  Herculaneum,  and  was  probably  buried 
with  that  city  in  an  eruption  of  Vesuvius,  which  happened 
during  the  reign  of  Titus.  In  the  excavations  which  the  mod- 
erns have  made  into  the  earth  which  covers  that  city,  these 
rolls  of  papyri,  nearly  1700  in  number,  were  found  in  a  house, 
the  roof  and  floors  of  which  had  been  crushed  in  by  the  sub- 
stances ejected  from  the  volcano.  The  rolls  were  found  in  a 
stat6  so  near  to  decomposition  that  the  least  violence  causes 
them  to  break  and  crumble  ;  their  color  is  so  nearly  black  that 
the  characters  are  distinguishable  from  the  paper  only  by  a 
slight  shade  of  difference ;  and  the  whole  roll  is  cemented  to- 
gether so  as  not  to  be  separable  into  layers  without  great  difficulty. 
This  state  has  been  supposed  to  be  produced  by  the  carbon- 
ization, or  converting  into  coal,  of  the  papyri,  by  the  heat  of  the 
ashes  and  lava,  in  which  they  were  buried.  Sir  Humphrey  Davy, 
however,  has  given  a  different  opinion  on  the  state  of  these 
manuscripts.  He  supposes  that  their  present  condition  is  not 
the  result  of  carbonization  or  of  heat  applied  to  them,  but  is  the 


THE   ARTS   OF   WRITING    AND  PRINTING. 


57 


consequence  of  their  remaining  for  so  many  ages  under  ground, 
until  the  vegetable  matter  of  which  they  are  composed,  has  un- 
dergone a  spontaneous  change,  and  become  converted  into  a 
substance  analogous  to  peat,  or  Bovey  coal.  This  conclusion 
is  the  result  of  chemical  examination,  and  is  likewise  inferred 
from  the  fact  that  some  specimens  of  gilding,  and  of  vermillion, 
which  remained  on  the  walls  of  the  apartment,  were  not  chang- 
ed in  color,  which  could  not  have  been  the  case,  had  the  heat 
been  sufficient  to  convert  vegetable  matter  into  charcoal. 

About  ninety  of  these  manuscripts  have  been  unrolled  by  a 
very  tedious  process,  which  consists  in  glueing  pieces  of  gold 
beaters'  skin  to  the  outside  of  the  rolls,  and  suffering  them  to 
dry  on.  They  are  then  gradually  raised  by  means  of  screws, 
lifting  with  them  a  layer  of  the  papyrus,  which  is  copied  and 
the  process  renewed.  Several  days,  in  this  way,  are  requisite 
for  a  single  page.  Sir  Humphrey  Davy  thinks  a  more  expedi- 
tious way  might  be  adopted  by  subjecting  the  rolls  to  the  action 
of  a  chemical  solvent,  capable  of  destroying  the  adhesion  of 
the  folds  to  each  other.  He  supposes  that  of  the  manuscripts 
which,  remain  not  more  than  from  eighty  to  one  hundred  and 
twenty  are  in  a  state  to  be  unrolled,  the  rest  being  too  much 
defaced,  by  crushing  or  otherwise,  to  render  it  probable  they  will 
ever  be  decyphered. 

Parchment. — Next  to  the  papyrus,  the  skins  of  animals,  in 
the  form  of  parchment  and  vellum,  w^ere  extensively  used  for 
writing,  by  the  ancients,  from  a  remote  period.  When 
Eumenes,  or  Attains,  attempted  to  found  a  library  at  Pergamus, 
200  years  B.  C,  which  should  rival  the  famous  Alexandrian  li- 
brary, one  of  the  Ptolemies,  then  king  of  Egypt,  jealous  of  his 
success,  made  a  decree  prohibiting  the  exportation  of  papyrus. 
The  inhabitants  of  Pergamus  set  about  manufacturing  parch- 
ment as  a  substitute,  and  formed  their  library  principally  of 
manuscripts  on  this  material ;  whence  it  was  known  among  the 
Latins  by  the  name  of  Pergamena.  The  term  membrana  was 
also  applied  by  them  to  parchment. 

Paper. — Paper  like  that  used  at  the  present  day,  composed 
of  flexible  fibres  reduced  to  a  pulp  by  minute  division,  and 
8 


58 


THE  ARTS   OF  WRITING  AND  PRINTING. 


cemented  into  sheets  by  means  of  size  or  glue,  began  to  be 
known  in  the  East  in  the  beginning  of  the  tenth  century.  It 
was  first  composed  of  cotton  or  silk  and  called  homhycina,  and 
was  not  made  from  linen  rags  until  the  fourteenth  century. 
Coarse  brown  paper  was  first  manufactured  in  England  in  1588  ; 
writing  and  printing  paper  in  that  country  not  till  1690,  previous- 
ly to  which,  it  was  imported  from  the  continent. 

Instruments, — While  writing  was  practised  upon  hard  sub- 
stances, as  stone  and  metal,  a  hard  metallic  point  was  the  instru- 
ment with  which  letters  were  formed.  The  stylus,  which  the 
Romans  employed  for  WTiting  on  brass  tablets  covered  with  wax, 
was  acute  at  one  end  for  writing,  and  flattened  or  blunt  at  the 
other,  for  erasing  what  was  written.  For  writing  in  colored 
fluids,  or  ink,  the  calamus  w^as  used,  a  reed  sharpened  at  the 
point,  and  split  like  our  pens.  Quills  were  not  introduced  till 
the  fourth  or  sixth  century.  ^ 

Some  of  the  eastern  nations  still  write  with  reeds,  canes,  and 
bamboos,  instead  of  quills.  The  Chinese  write  with  small 
brushes  like  camel's  hair  pencils. 

Inks. — The  ink  of  the  ancients  consisted  of  a  carbonaceous 
substance,  such  as  lampblack,  soot,  or  pulverized  coal,  united 
with  a  viscid  or  gummy  liquid.  The  black  liquor  of  the  cuttle 
fish  (Sepia)  was  sometimes  employed.  Colored  inks  of  Ver- 
million, red  lead,  and  purple,  were  also  used.  The  eastern 
emperors  signed  their  edicts  with  red  ink,  the  use  of  which  was 
prohibited  to  others,  under  pain  of  death. 

Modern  ink  is  essentially  a  tanno-gallate  of  iron  suspended 
by  mucilage.  It  may  be  made  from  salts  of  iron,  and  infusions 
of  various  astringent  vegetables.  But  as  many  products  of 
this  kind  are  apt  to  fade  by  time,  it  is  not  safe  to  trust  to  any 
which  have  not  had  the  testimony  of  long  experience  in  their 

*  The  earliest  notice  of  the  use  of  quills,  is  by  an  anonymous  author  of  the 
life  of  Constantius,  who  says  that  Theodoric,  the  Ostrogothic  king  of  Rome, 
was  so  illiterate,  and  so  dull  of  intellect,  that,  during  the  ten  years  of  his  reign, 
he  could  not  learn  four  letters  to  sign  at  the  bottom  of  his  edicts ;  so  that 
they  were  cut  for  him  in  a  plate  of  gold,  through  which  he  traced  the  letters 
with  a  quill.  One  of  the  oldest  certain  mentions  of  the  use  of  quills,  is  by  Isi- 
dore, who  died  in  636. 


THE   ARTS   OF   WRITING   AND   PRINTING.  59 

favor.  The  best  materials  are  the  nutgall  and  sulphate  of  iron, 
with  gum  arabic.  Other  ingredients  are  sometimes  added, 
such  as  logwood,  sulphate  of  copper,  and  sugar.  When  ink 
fades,  it  is  commonly  from  the  fugitive  nature  of  the  gallic  acid 
and  tannin  ;  and  it  may  be  revived  by  moistening  the  page  with 
a  fresh  infusion  of  galls.  When  ink  grows  thin  from  freezing, 
or  dilution,  so  that  its  particles  subside,  they  may  again  be  sus- 
pended, by  agitating  it  with  sugar,  or  gum.  If  writing  with 
common  ink  has  been  obliterated  by  chlorine,  it  may  be  again 
rendered  legible,  by  the  vapor,  or  solution,  of  sulphuret  of  am- 
monia. Indelible  ink  is  produced  by  writing  with  dissolved  ni- 
trate of  silver  on  a  surface  impregnated  with  carbonate  of  soda. 

Copying  Machines. — Various  modes  have  been  devised,  fcM* 
making  extemporaneous  copies  of  written  pages.  Dr  Frank- 
lin's method  consisted  in  covering  the  writing,  while  yet  moist, 
with  fine  powdered  emery  ;  and  afterwards  passing  the  sheet 
through  a  press,  in  contact  with  a  plate  of  pewter,  or  copper ; 
which  thus  became  marked  with  the  letters,  so  as  to  yield  im- 
pressions, as  in  the  common  mode  of  copperplate  printing. 
Mr  Watt's  copying  machine,  consists  of  a  press,  in  which  a 
thin,  bibulous  paper,  previously  moistened,  is  forced  into  close 
contact  with  the  page,  while  newly  written.  A  part  of  the 
ink,  sufficient  to  produce  legible  characters,  is  thus  transferred 
to  the  thin  paper.  The  writing  is  of  course  reversed,  but  the 
thinness  of  the  paper  permits  it  to  be  read  on  the  opposite  side, 
which  restores  the  order  of  the  letters.  Mr  Hawkins'  poly- 
graph, is  a  machine  carrying  two  or  more  pens  in  different  pla- 
ces, which  are  so  connected  as  to  pursue  a  similar  path  with 
each  other,  and  execute  two  or  more  copies  at  once.  Lithog- 
raphy likewise  offers  a  ready  method  of  multiplying  copies. 

PRINTING. 

The  art  of  printing,  as  it  is  now  practised,  by  the  composition 
of  moveable  types,  is  so  simple  and  obvious  in  its  principles, 
that  it  is  truly  wonderful  the  process  was  not  earher  known. 


00  THE   ARTS   OF   WRITING   AND  PRINTING. 

The  ancients  many  times  made  near  approaches  to  the  discov- 
ery, but  by  some  singular  fatality,  they  were  kept  from  its  prof- 
itable use.  Arts  far  more  curious,  and  sciences  far  more  diffi- 
cult, were  known,  and  carried  to  perfection,  by  the  patient  in- 
dustry of  the  ingenious  and  enterprising  in  former  times.  But 
this  art,  which  was  to  give  permanency  to  all  the  rest,  and  which 
now  seems  to  be  at  the  root  of  all  human  knowledge,  was  nev- 
er in  useful  operation  in  Europe  until  three  or  four  centuries 
ago. 

Types. — Printing  at  the  present  day  is  executed  with  move- 
able types,  which  are  oblong  square  pieces  of  metal,  each  bear- 
ing a  letter  in  relief  at  one  extremity.  The  metal  of  which 
they  are  made,  is  an  alloy,  which  consists  essentially  of  lead 
and  antimony.  The  lead  is  selected  in  preference  to  other 
metals,  because  it  is  fusible  at  a  low  temperature,  and  retains 
accurately  the  shape  it  receives  from  the  mould.  But  as  lead 
alone  is  too  soft  to  sustain  the  friction  and  pressure  to  which  it 
is  liable  in  use,  about  a  fifth  part  of  antimony  is  added.  This 
gives  it  a  superior  hardness  when  cast,  and  as  this  alloy  has  the 
property  of  shrinking  less  than  most  other  metals  as  it  cools, 
the  type  receives  all  the  sharpness  and  finish,  which  it  can  ac- 
quire, by  filling  every  part  of  the  mould.  In  making  types,  the 
letter  is  first  cut  by  an  artist  upon  the  end  of  a  steel  punch, 
answering  to  the  shape  of  the  intended  type.  This  punch  is 
driven  into  a  piece  of  copper,  which  forms  the  matrix  or  bottom 
of  the  mould  intended  to  produce  the  letter.  As  many  vari- 
eties of  punches  must  be  made  of  steel,  as  there  are  sizes  and 
species  of  characters  required.  In  casting,  the  types  are  form- 
ed with  great  rapidity,  owing  to  the  quickness  with  which  the 
metal  cools.  An  expert  operator  will  make  2000  or  3000 
types  in  a  day.  Some  machines  have  been  introduced,  for 
casting  types,  which  operate  with  much  greater  rapidity.  The 
characters  upon  types  are  of  course  reversed,  so  that  in  ar- 
ranging them  for  the  press,  the  compositor,  or  printer  who  sets 
the  types,  begins  at  die  right  hand  of  each  line. 


THE   ARTS   OF   WRITING   AND   PRINTING.  Gl 

Case. — Before  the  types  are  applied  to  use,  they  are  arranged 
ill  the  cells,  or  compartments,  of  a  long  wooden  receptacle,  call- 
ed a  case  ;  each  species  of  letter,  character,  or  space,  by  it- 
self. In  arranging  the  compartments,  the  collections  of  letters 
do  not  succeed  each  other  in  alphabetical  order,  nor  are  they 
all  of  equal  size.  Those  letters  which  occur  most  frequently 
in  printing,  are  required  in  greater  numbers.  They  are  there- 
fore made  to  occupy  the  largest  compartments,  and  are  placed 
nearest  to  the  compositor.  Thus  the  letter  e,  which  is  of  fre- 
quent occurrence,  fills  a  large  compartment,  and  is  nearest  the 
compositor,  while  the  letter  x,  which  occurs  much  less  frequent- 
ly, is  provided  in  small  numbers,  and  placed  at  the  extremity 
of  the  case.  In  a  hill  or  collection  of  types  of  the  size  called 
pica,  weighing  in  all  800  pounds,  the  number  of  the  letter  e  is 
12000;  oft,  9000;  of  a,  8500;  of  i,  n,  o,  and  s,  8000  each; 
of  c  there  are  3000  ;  of  b  1600  ;  k  800  ;  x  400 ;  z  200.  This  * 
is  for  the  English  language.  In  other  languages,  the  compar- 
ative frequency  must  be  different. 

Sizes. — Difierent  names  are  given  to  the  various  sizes  of 
types,  of  which  the  following  are  most  employed  in  common 
book  printing. 

Pica. — a  bcdefghijklmnopqrstu 
Small  Pica. — a  bcdefghijklmnopqrstuvw 
Long  Primer. — a  bcdefghij  klmnopqrstuvw 
Bourgeois. — a  bcdefghij  klmnopqrstuvwxyz 
Brevier. — a  bcdefghij  klmnopqrstuvwxyz 
Minion. — a  bcdefghijklmnopqrstuvwxyz 
Nonpareil. — a  bcdefghijklmnopqrstuvwxyz 

C&mposing. — The  compositor  is  first  provided  with  an  in- 
strument called  the  composing  stick.  This  is  a  plate,  common- 
ly of  iron  or  brass,  surrounded  with  ledges,  one  of  which  is 
moveable,  so  that  the  length  of  the  lines  may  be  adjusted  to 
the  width  of  the  page.  The  compositor  selects  from  their  pla- 
ces the  letters  successively,  to  constitute  the  first  word,  which 


63  THE   ARTS   OF  WRITING   AND  PRINTING. 

are  arranged  in  an  inverted  order  from  that  in  which  they  are 
to  appear  on  the  printed  page,  beginning  at  the  right.  At  the 
end  of  the  word  a  quadrat  is  inserted  to  produce  a  space  be- 
tween this  word  and  the  next  following.  The  quadrats,  of 
w^hich  there  are  various  kinds,  differently  named  from  their 
width,  are  blunt  types,  bearing  no  letter  on  their  extremities.  Li 
printing,  they  do  not  come  up  to  the  surface,  and  of  course 
yield  no  impression.  As  the  beauty  of  the  page  depends  upon 
the  evenness  of  the  margin  produced  by  the  equality  of  the 
lines,  these  quadrats  are  used  to  swell  out  the  shorter  lines  and 
bring  them  to  an  equality  with  the  rest.  When  one  line  is  finished, 
the  printer  shifts  the  rule  from  below  it  to  the  top,  and  commen- 
ces setting  the  types  for  a  second  line.  The  rule  is  a  thin 
brass  plate  used  to  make  the  types  slide  easily  and  not  catch 
upon  the  line  below  them. 

The  quickness  with  which  an  expert  compositor  advances  in 
his  work,  is  greater  than  would  appear  possible  from  a  first  con- 
sideration of  the  subject.  The  familiarity  with  the  situations 
of  the  letters  and  their  arrangement,  produced  by  long  habit,  is 
such,  that  to  select  the  types  and  place  them,  does  not  require 
a  thought  to  be  bestowed  on  the  process.  It  is  only  necessary 
to  perceive  the  meaning  of  each  w^ord,  and  the  putting  it  togeth- 
er follows  as  mechanically  as  writing.  It  is  even  possible  for  a 
printer  to  compose  in  the  dark,  for  the  exact  situation  of  each 
letter  in  the  case  before  him  being  known,  and  the  upper  side 
of  each  being  known  by  notches  in  the  type,  they  can  be  se- 
lected and  arranged  by  the  sense  of  feeling  alone. 

Imposing. — When  a  sufficient  number  of  lines,  say  six  or 
eight,  are  formed  in  the  composing  stick,  they  are  emptied  into 
another  instrument  called  the  galley,  w^hich  is  a  flat  board  or 
plate,  partly  or  wholly  surrounded  by  a  rim  In  this  galley, 
the  types  are  accumulated,  generally  in  the  form  of  long  col- 
umns, which  are  afterwards  divided  into  pages,  each  page  be- 
ing tied  together  w-th  a  string  to  prevent  the  types  from  falling 
asunder.  When  a  sufficient  number  of  pages  are  complet- 
ed to  constitute  what  is  called  a  forme,  or  in  other  words,  to 


THE   ARTS   OF   WRITING   AND   PRINTING.  G3 

fill  one  side  of  a  sheet,  they  are  arranged  upon  an  imposing 
stone,  and  strongly  locked  up,  or  wedged  together,  in  an  iron 
frame  denominated  a  chase,  to  prepare  them  for  the  press. 

Signatures. — A  sheet  intended  for  a  folio,  has  two  pages  on 
a  side,  and  will  form  two  leaves.  A  quarto  has  four ;  an  octa- 
vo, eight ;  a  duodecimo,  twelve,  &;c.  These  pages  are  so  arrang- 
ed in  the  forme,  that  in  the  impression,  they  will  assume  their 
true  order,  after  the  sheet  is  folded.  The  sheets  are  marked 
at  the  bottom  of  certain  pages  with  successive  numbers,  or  capi- 
tal letters  ;  the  object  of  which  is  to  afford  the  necessary  in- 
structions for  the  order  of  folding  and  gathering  them.  These 
are  called  signatures. 

Correcting  the  Press. — The  first  impression  taken  from  the 
types  is  called  a  proof.  This  is  carefully  read  over  and  the  er- 
rors and  inaccuracies  marked.  To  correct  them,  the  w^edges 
or  quoins  are  knocked  out  so  as  to  loosen  the  types,  the  erro- 
neous letters  are  drawn  out,  and  the  proper  ones  substituted, 
and  the  whole  is  again  wedged  into  the  frame. 

Many  of  the  errors  of  the  press,  which  remain  uncorrected 
in  books,  arise  from  a  want  of  understanding,  between  the  au- 
thor, or  corrector,  and  the  printer,  in  the  characters  used  in 
correction.  It  is  not  enough  that  the  author  should  detect 
these  errors  and  note  them  in  the  margin.  He  must  express,  by 
intelligible  marks,  how  these  defects  are  to  be  altered,  and  un- 
less he  uses  such  marks  as  are  employed  by  printers  themselves, 
his  attempts  at  correctness  will  be  defeated.  Every  person 
who  has  occasion  to  appear  in  print,  should  first  know  how  to 
correct  the  press.  * 

*  If  the  error  is  confined  to  a  letter  or  word,  it  is  easily  corrected.  But  if  it 
involves  the  addition  or  erasure  of  a  sentence  or  a  number  of  lines,  the  cor- 
rection is  more  difficult.  The  whole  forme  must  be  deranged,  and  as  the  add- 
ing or  expunging  of  lines  affects  the  length  of  the  page,  it  must  be  adjusted 
at  the  expense  of  the  next  following  page  ;  so  that  all  the  subsequent  pages 
may  be  disturbed,  before  the  necessary  correctness  is  obtained.  An  author 
who  corrects  the  press  for  his  own  works,  will  very  much  abridge  the  labor 
of  the  printer,  if,  in  all  cases  of  an  erased  word,  he  will  substitute  another  of 
nearly  the  same  length  in  its  neighborhood,  or,  if  a  new  word  is  added,  by  strik- 
gn  out  one  in  the  paragraph  which  can  be  better  spared. 


64  THE   ARTS   OF   WRTTING   AND  PRINTING. 

The  following  signs  for  correcting  the  press,  are  em- 
ployed by  printers  themselves. 

When  a  wrong  letter  is  discovered,  a  line  is  drawn 
through  it,  and  the  true  letter  written  in  the  margin,  thus ; 

To  be,  or  not  to  be,  that  iiji  the  question. 

If  a  letter  is  found  to  be  omitted,  a  caret  is  placed 
under  its  place,  and  the  letter  written  in  the  margin,  thus; 

To  be,  or  not  to  be,  tht  is  the  question. 

If  a  superfluous  letter  is  detected,  it  is  crossed  out, 
and  a  character  which  stands  for  dele^  introduced  in 
the  margin. 

To  be,  or  not  to<j)  be,  that  is  the  question. 

If  two  words  are  improperly  joined  together,  a  char- 
acter indicating  a  space,  or  quadrat,  is  used. 

To  be,  or  not  tobe,  that  is  the  question. 

A 

If  syllables  of  the  same  word  are  improperly  separat- 
ed, they  are  joined  by  a  horizontal  parenthesis. 

To  be,  or  not  to  be,  that  is  the  ques  tion. 

When  words  are  found  to  be  transposed,  they  are 
connected  by  a  curved  line,  and  the  letters  tr.  written 
in  the  margin. 

To  be,  or  not  to  be,  (IsXthat)  the  question. 

When  a  letter  is  inverted,  it  is  expressed  by  a  char- 
acter of  this  sort  in  the  margin. 

Marks  of  punctuation,  if  of  small  size,  are  inclosed 
in  circles,  thus ; 

A  comma  is  placed  after  a  short  stroke,  an  apostrophe 
before  it. 


THE  ARTS   OF   WRITING   AND   PRINTING.  05 

Words  intended  to  be  printed  in  Italics,  are  marked  beneath 
with  a  single  line  ;  if  in  small  capitals,  with  two  lines  ;  and  if  in 
large  capitals,  with  three.  Thus  a  line  marked  in  this  man- 
ner. 

Oh  thou,  in  Hellas  deemed  of  heavenly  birth. 

would  be  printed  thus; — 

Oh  thou  in  HELLAS  deemed  of  heavenly  birth. 

In  correcting  with  these  marks,  the  abbreviations  Ital,  Rom. 
Caps.  &c.  should  also  be  WTitten  in  the  margin. 

Corrections  themselves  sometimes  require  to  be  corrected. 
Thus  if  a  word  has  been  improperly  altered,  and  it  is  after- 
wards thought  best  to  retain  it,  dots  are  placed  beneath  and 
the  word  stet  written  in  the  margin. 

When  lines  are  crooked,  or  letters  have  been  disturbed  from 
their  places,  or  blemishes  appear,  it  is  sufficient  to  call  the  at- 
tention of  the  printer,  by  a  dash  of  the  pen,  at  the  place. 

Press  Work. — After  the  sheet  is  corrected  and  revised,  it  is 
then  ready  for  the  press,  to  which  it  is  accordingly  transferred. 
The  ink  is  first  applied  over  the  whole  surface  of  the  types ; 
the  paper,  previously  moistened,  is  then  laid  down  upon  them, 
the  whole  is  passed  under  the  press,  and  the  paper  being  brought 
into  forcible  contact  with  the  types,  receives  from  their  surface 
the  ink  necessary  for  a  distinct  impression.  Printers'  ink  is 
composed  chiefly  of  lampblack  and  oil  inspissated  by  boiling  and 
and  burning.  Oil  is  necessary,  that  the  ink  may  not  dry  during 
the  operation,  and  it  is  reduced  by  boiling,  to  prevent  it  from 
spreading  on  the  paper.  It  is  applied  to  the  types  by  large 
elastic  balls  made  of  leather  and  stuffed  with  wool,  or  by  elas- 
tic rollers,  like  those  used  in  printing  machines. 

Printing  Press. — The  common  or  old  printing  press,  derives 
its  powder  from  a  screw,  wdiich  is  turned  by  a  lever,  and  acts 
perpendicularly  on  the  platten,  or  level  part,  which  transmits  the 
pressure.    Various  improvements  have  been  made  in  the  pript- 


9 


66 


THE   ARTS   OF  WRITING  AND  PRINTING. 


ing  press,  by  Lord  Stanhope,  and  other  inventors,  in  most  of 
which  a  cast  iron  frame  is  substituted  for  a  wooden  one,  being 
more  inflexible  ;  and  a  combination  of  levers  is  used,  so  arranged 
as  to  cause  the  platten  to  descend  with  decreasing  rapidity,  and 
consequently  with  increasing  force,  till  it  exerts  the  greatest 
power  at  the  moment  of  contact  of  the  paper  witli  the  types. 

Stereotyping, — In  stereotype  printing,  instead  of  moveable 
types,  blocks  or  plates  are  used,  each  containing  all  the  charac- 
ters requisite  to  form  a  page.  The  process  of  stereotyping  is 
simple.  A  page  of  any  work  proposed  to  be  stereotyped,  is 
set  up  in  the  usual  manner  with  moveable  types.  From  this 
page,  when  corrected,  a  mould  in  plaster,  is  taken  off,  and  from 
this  mould  a  plate  of  type  metal  is  cast,  having  all  the  charac- 
ters in  relief,  and  being  a  fac-simile  of  the  original  page.  From 
this  plate  the  printing  is  executed,  and  there  must  be  of  course, 
as  many  plates  cast,  as  there  are  pages  in  the  book  to  be  print- 
ed. It  will  thus  be  seen,  from  the  accounts  already  given,  that 
the  stereotyped  letter  press,  constitutes  the  sixth  time  that  the 
character  has  been  formed,  viz.  1,  in  the  steel  punch  ;  2,  in 
the  matrix  ;  3,  in  the  moveable  type ;  4,  in  the  plaster  cast ;  5, 
in  the  stereotyped  character,  and  6,  in  the  printed  page. 

The  plaster  used  for  forming  the  moulds  is  pulverized  gyp- 
sum, dried  by  heat,  and  mixed  with  water;  to  which  is  added 
a  little  whiting  to  diminish  the  tendency  of  the  plaster  to  shrink 
and  crack.  After  the  forme  of  types  has  been  slightly  oiled, 
and  surrounded  w4th  a  brass  frame,  fluid  plaster  is  applied  over 
the  surface  with  a  brush  or  roller,  so  as  to  fill  every  cavity  of 
the  letters.  A  quantity  of  plaster  mixed  with  water  to  the 
consistence  of  cream,  is  then  poured  on  the  type,  and  the  su- 
perfluous part  scraped  off.  When  the  plaster  has  become  hard, 
it  is  lifted  off  by  the  frame  and  detached  from  it.  It  is  then 
baked  to  dryness  in  an  oven,  and  when  quite  hot,  it  is  placed 
in  an  iron  box  or  casting  pot,  which  has  also  been  heated  in  an 
oven.  The  box  is  now  plunged  into  a  large  pot  of  melted  type 
metal,  and  kept  about  ten  minutes  under  the  surface,  in  order 
that  the  weight  of  the  metal  may  force  it  into  all  the  finer  parts 


THE  ARTS   OF  WRITING  AND  PRINTING. 


67 


of  the  letters.  The  whole  is  then  cooled,  the  mould  broken 
and  washed  off,  and  the  back  of  the  plate  turned  smooth  in  a 
lathe,  or  planed  by  a  machine.  The  earlier  stereotype  found- 
ers, as  Didot  and  others,  formed  their  moulds  with  a  soft  met- 
al, or  a  metal  at  the  point  of  congelation,  instead  of  plaster. 

Stereotype  printing  is  chiefly  useful  for  standard  and  classi- 
cal works,  for  which  there  is  a  regular  demand,  and  of  which 
the  successive  editions  require  no  alteration.  It  is  now  execut- 
ed with  such  increased  economy,  as  to  be  appHcable  to  works 
even  of  less  durability. 

Machine  Printing. — Printing  by  machinery,  is  one  of  the 
latest  achievments  of  art,  having  had  its  origin  within  the  pres- 
ent century.  It  has  produced  a  very  great  improvement  in  the 
expedition  with  which  work  is  executed,  and  is  now  extensive- 
ly applied  to  the  printing  of  newspapers  and  even  of  books. 
Various  machines  are  already  introduced  into  use,  most  of 
which  perform  the  processes  of  inking  the  types,  conveying  the 
paper,  and  giving  the  impression.  For  distributing  the  ink  on 
the  types,  elastic  cylinders  are  employed,  called  inking  rollers, 
made  of  a  composition  of  glue  and  treacle,  which  combines 
the  properties  of  smoothness,  elasticity,  and  sufficient  durability. 
These  transmit  the  ink  to  the  types  by  rolling  over  their  surface. 
The  impression  is  performed  in  most  of  the  English  machines, 
by  large  cylinders  which  revolve  upon  the  types,  having  the 
sheet  of  paper  confined  to  their  surface  by  bands  of  tape.  The 
types  are  arranged  in  some  machines  in  the  common  flat  form, 
in  others,  the  characters  are  placed  in  a  convex  form  upon  the 
surface  of  cylinders.  To  produce  the  latter  effect  Mr  Nich- 
olson proposed  to  cast  the  body  of  the  types  with  a  tapering  or 
wedge  form,  like  the  stones  of  an  arch,  but  Mr  Cowper  has 
produced  the  same  object  more  expeditiously,  by  curving  stere- 
otype plates  into  the  required  shape.  Messrs  Donkin  and  Ba- 
con placed  their  types  on  the  four  sides  of  a  revolving  prism, 
while  the  ink  was  applied  by  a  roller  which  rose  and  fell  with 
the  irregularities  of  the  prism,  and  the  sheet  was  wrapped  on 
another  prism  so  formed  as  to  meet  the  surfaces  of  the  first. 


68 


THE   ARTS   OF   WRITING   AND  PRINTING. 


A  common  printing  press,  gives  about  250  impressions  per  hour, 
whereas  of  the  Times,  a  London  newspaper,  printed  by  Apple- 
gath  and  Cow^per's  machine,  it  is  stated  that  4000  per  hour  are 
printed  on  one  side.  The  first  ivorJcing  machine  which  printed 
by  steam,  was  erected  by  Mr  Koenig,  in  1814. 

In  this  country,  Treadwell's  power  press  is  the  machine  most 
employed.  In  this  invention,  the  types  are  inked  by  elastic 
rollers,  and  the  distribution  of  the  ink  rendered  equal,  by  a  re- 
volving table  which  passes  in  contact  with  the  rollers.  The 
impressions  are  made  by  a  flat  surface  or  platten,  instead  of  a 
cyhnder,  so  that  cleaner  and  better  impressions  are  supposed 
to  be  obtained  from  it,  than  from  any  other  machine. 

History, — The  art  of  printing  was  first  carried  into  success- 
ful operation,  a  httle  before  the  middle  of  the  fifteenth  century. 
The  honor  of  having  given  birth  to  the  invention,  is  claimed  by 
the  chies  of  Haerlem,  Mentz,  and  Strasburgh,  in  each  of  which 
the  art  was  successfully  practised  at  an  early  period.  The  best 
authors,  however,  agree  in  considering  that  the  original  inventor 
of  printing,  was  Laurentius,  otherwise  called  Coster,  of  Haer- 
lem, who  made  his  first  attempt  in  1430,  with  separate  wooden 
types.  He  died  ten  years  after,  having  printed  the  'Horarium,' 
the  '  Speculum  Belgicum,'  and  two  different  editions  of  Dona- 
tus,  which  w^ere  tKe  first  books.  After  his  death,  printing  was 
carried  on  at  Mentz,  by  John  Gensfleisch,  who  had  possessed 
himself  of  some  of  Laurentius's  types,  and  who  like  his  master 
printed  in  wood.  This  man,  with  the  assistance  of  his  brother, 
who  is  usually  called  Guttenberg,  afterward  invented  cut  metal 
types,  with  which  was  printed  the  earhest  edition  of  the  bible. 
This  edition  appeared  in  1450,  having  taken  seven  or  eight 
years  for  its  completion. 

Guttenberg  used  none  but  wooden  or  cut  metal  types.  The 
art  received  its  consummation  soon  after,  from  Peter  Schoeffer, 
who  invented  the  mode  of  casting  types  in  matrices.  The  cel- 
ebrated Faustus,  who  has  often  been  considered  as  the  inventor 
of  printing,  was  in  partnership  with  the  persons  already  men- 
tioned, and  furnished  funds  to  defray  the  expenses  of  the  en- 


THE  ARTS   OF   WRITING   AND   PRINTING.  C9 

terprise,  the  processes  being  kept  secret.  The  well  known 
tale  of  the  practice  of  necromancy,  by  Faustus,  was  owing  to 
his  carrying  a  parcel  of  his  bibles  to  Paris,  and  offering  them 
for  sale  as  manuscripts.  The  French  finding  so  great  a  num- 
ber of  books  resembling  each  other  exactly,  and  more  so  than 
it  was  possible  for  any  chirographer  to  have  made  them,  conclud- 
ed there  was  witchcraft  in  the  case,  and  by  inditing  Faustus  as 
a  conjuror,  compelled  him  to  disclose  the  secret  in  his  own 
defence. 

After  the  invention  of  printing  with  fusible  types,  it  spread 
rapidly  into  many  of  the  cities  of  Europe,  and  was  practised 
at  an  early  period  at  Tours,  Rome,  and  Venice.  It  was  first 
carried  on  in  England  by  Caxton  and  Corsellis,  about  1470, 
and  the  earliest  press  was  estabhshed  at  Oxford. 

It  is  remarkable  that  this  important  art,  after  becoming  once 
estabhshed,  underwent  no  essential  improvement  for  a  period  of 
more  than  300  years.  Having  remained  stationary  for  three 
centuries,  it  has  received  a  fresh  impulse  within  the  last  few 
years,  by  the  invention  of  stereotyping,  and  of  printing  by  ma- 
chinery. 

Although  printing  with  moveable  types  is  exclusively  a  mod- 
ern art,  yet  there  are  some  steps  in  the  discovery,  which  have 
claim  to  greater  antiquity.  The  Chinese  have  printed  with 
their  characters,  for  more  than  900  years,  but  as  the  nature 
of  this  character  requires  that  much  should  be  expressed  by  a 
single  figure,  they  are  obliged  to  cut  each  character  with  all  its 
complications  in  a  block  of  wood,  so  that  their  method  resem- 
bles a  hmited  kind  of  stereotype  printing. 

Among  the  relics  of  ancient  Rome,  there  have  been  found 
letters  cut  in  brass  and  raised  above  the  surface  exactly  like  our 
printing  types.  Some  of  these  contain  the  names  of  individu- 
als, and  from  their  shape  and  appendages,  were  evidently  used 
for  the  purpose  of  signature,  the  letters  being  small,  smooth, 
and  even,  while  the  ground  beneath  them  is  unequal,  and  rough, 
so  that  they  must  have  been  employed,  not  for  impressions  into 
soft  substances,  but  for  printing  with  colored  liquids,  on  a  sur- 


TO  THE  ARTS  OF  WRITING  AND  PRINTING. 

face  like  parchment  or  paper.  Had  the  individuals,  whose 
names  were  thus  printed,  been  visited  with  the  thought  that  by 
separating  the  letters,  they  might  print  the  name  of  another,  it 
is  probable  that  the  art  would  have  been  at  once  discovered, 
and  that  the  dark  ages  might  never  have  happened. 


Works  of  Reference. — Astle,  Origin  and  Progress  of  Writing, 
4to.  London,  1803  ; — Fry,  Pantographia,  4to.  London,  1799 ; — Town- 
liET,  Illustrations  of  Biblical  Literature,  1821 ; — Stower,  Printer's 
Grammar,  8vo.  London,  1808; — Thomas,  History  of  Printing,  8vo. 
Worcester,  U.  S.  1810; — Meerman,  Origines  Typographic  HagcB 
1765; — CowPER,  in  Brando's  Journal  of  Science,  1828 ; — Hansard, 
Typographia,  large  8vo.  1825. 


CHAPTER  IV. 


ARTS  OF  DESIGNING  AND  PAINTING. 

Designing  is  the  art  of  deline^iting  or  drawing  the  appear- 
ance of  natural  objects,  by  lines  on  a  plane  surface.*  Paint- 
ing may  be  considered  as  the  same  art,  so  extended  as  to  in- 
clude coloring,  and  whatever  else  is  necessary  to  produce  com- 
plete or  finished  resemblances.  It  is  obvious,  that  if  the  art  of 
painting  was  carried  to  perfection,  these  resemblances  could  not 
be  told  at  sight,  from  their  originals  ;  since  we  are  supposed  to 
discern  objects  by  the  medium  of  their  pictures  painted  on  the 
retina  of  the  eye,  and  since  a  polished  mirror  gives  us  every 
appearance  of  reality,  in  the  forms  reflected  from  it,  though 
they  all  proceed  from  the  same  plane. 

Divisions, — To  produce  perfect  representations  of  nature, 
three  things  must  receive  attention,  and  the  study  of  these  may 
be  considered  as  constituting  distinct  departments  in  the  art  of 
painting.  These  are,  1 .  The  perspective,  by  which  the  outlines 
of  figures  are  placed  on  the  picture  in  situations  depending  on 
their  position  in  regard  to  the  eye.  2.  The  chiaro  oscuro,  or 
light  and  shade,  by  which  the  prominence  and  depression  of 
different  parts  of  the  piece,  are  made  to  appear.  3.  The  color- 
ing, by  which  the  hues  and  tints  of  the  painting  are  made  con- 
formable to  those  of  the  original. 

Perspective. — Perspective  is  the  art  of  delineating  the  out- 
lines of  objects  on  any  given  surface,  as  they  w^ould  appear  to 
the  eye,  if  that  surface  were  transparent,  and  the  objects  them- 
selves were  seen  through  it  from  a  fixed  position.  It  is  the 
foundation  of  correctness  in  painting,  and  a  strict  attention  to 


*  Rees's  Cyclopedia. 


72 


ARTS  OF  DESIGNING  AND  PAINTING. 


its  rules,  is  indispensable  to  perfection  in  the  art.  The  first 
attempts  at  drawing,  have,  in  all  countries,  consisted  of  diagrams, 
and  sketches,  representing  merely  the  plans,  or  profiles  of  ob- 
jects, without  regard  to  their  perspective  relations.  But  a  con- 
tinued attention  to  their  actual  appearance  or  images,  combined 
with  the  application  of  a  few  geometrical  and  optical  principles, 
has  furnished  the  means  of  fixing  the  outlines  of  objects,  in 
their  true  situation  on  a  perspective  plane. 

If  we  look  through  a  window  at  a  mass  of  buildings,  or  any 
external  objects,  and  observe  that  part  of  the  glass  to  which 
each  object,  line,  or  point,  appears  opposite,  we  find  that  their 
apparent  situation  is  very  different  from  their  real.  We  find 
that  horizontal  lines  sometimes  appear  oblique,  or  even  perpen- 
dicular, that  circles,  in  certain  situations,  look  like  ellipses,  and 
squares,  like  trapezoids,  or  parallelograms.  High  objects  are 
seen  beneath  low  ones,  and  large  bodies  are  exceeded  in  appar- 
ent magnitude,  by  small  ones.  The  foundation  of  all  these  ap- 
pearances exists  in  the  rectilinear  motion  of  the  rays  of  light 
passing  from  the  object  to  the  eye. 

Field  of  Vision, — When  the  eye  is  fixed,  the  rays  entering 
it  from  the  whole  field  of  vision,  constitute  a  cone  having  its 
apex  in  the  eye.  The  field  presented  to  the  eye,  and  occupy- 
ing the  base  of  the  cone,  cannot  well  subtend  an  angle  of  more 
than  90  degrees,  and  we  cannot  have  a  convenient  and  agreea- 
ble view  of  a  field  occupying  more  than  60  degrees.  Even 
the  most  satisfactory  views  of  objects  are  obtained  at  such  dis- 
tances as  cause  them  to  subtend  an  angle  of  30  or  40  degrees. 
Panoramic  views  subtend  a  larger  angle  than  those  which  have 
been  specified,  and  of  course  cannot  be  taken  in  by  the  eye  at 
a  single  view.  It  becomes,  therefore,  necessary  to  take  suc- 
cessive views  with  the  eye,  in  different  directions. 

Distance  and  Foreshortening. — Of  objects  situated  within 
the  field  of  vision,  those  necessarily  appear  largest,  cceteris  pa- 
ribus, which  are  nearest  to  us,  because  they  subtend  a  larger 
angle  at  the  eye.  Objects  or  surfaces  situated  obliquely  in  re- 
gard to  the  axis  of  the  eye,  are  altered  in  apparent  shape  by 


ARTS  OF  DESIGNING   AND  PAINTING. 


73 


the  shortening  of  their  oblique  diameters.  This  is  what  is 
technically  called  foreshortening.  If  several  objects,  for  exam- 
ple, of  equal  size,  be  placed  at  different  distances,  and  in  differ- 
ent positions  [See  Plate  III.  Fig.  5.],  the  one  nearest  the  eye, 
as  X,  will  subtend  the  largest  angle,  and  its  comparative  length 
in  the  picture  will  be  represented  by  the  line  A  B.  The  ob- 
ject Y,  being  further  off,  subtends  a  smaller  angle,  and  will  be 
represented  by  the  hne  AC.  The  object  Z,  being  still  further 
removed,  and  also  foreshortened  by  its  oblique  position,  will 
produce  an  image  no  longer  than  from  A  to  D. 

A  simple  instrument  may  be  formed  by  any  person,  to  rep- 
resent the  effect  of  distance  and  of  foreshortening  in  perspec- 
tive. Let  four  straight,  stiff  wires  [PI.  III.  Fig.  6.]  be  connect- 
ed at  one  end.  A,  by  a  string  or  socket,  which  will  allow  them 
to  diverge.  Let  a  thin,  square  board,  or  tin  plate,  be  attached 
at  the  other  end,  at  C,  by  loops  at  its  four  corners,  through 
which  the  wires  pass.  Let  a  string  of  elastic  gum  be  placed 
around  the  wires  at  B,  about  half  way  between  A  and  C.  The 
elastic  string  will  represent  the  picture,  the  board  the  object, 
and  the  wires  the  rays  passing  from  the  object  to  the  eye  at  A. 
If  now  the  board  be  moved  upon  the  wires  toward  the  eye,  the 
elastic  string  will  be  extended,  or  the  picture  enlarged.  The 
reverse  will  happen,  if  the  board  be  carried  away  from  the  place 
of  the  eye.  The  board  may  also  be  turned  into  various  oblique 
positions,  and  the  elastic  string  will  represent  the  figure  produc- 
ed by  the  foreshortening. 

Definitions. — There  are  used  in  perspective  a  certain  num- 
ber of  terms  peculiar  to  the  art,  definitions  of  which  are  neces- 
sary to  an  intelhgent  use  of  them. 

The  original  object,  is  that  which  is  made  the  subject  of  the 
picture. 

Original  planes  or  li7ies,  are  the  surfaces  or  lines  of  original 
objects. 

The  point  of  view  is  the  situation  of  the  eye. 
The  point  of  sight  is  the  point  in  the  perspective  plane,  which 
is  nearest  to  the  eye.    As  far  as  the  picture  is  concerned,  these 
10 


74 


ARTS  OF  DESIGMNG  AND  PAINTING., 


two  points  coincide,  so  that  some  authors  have  used  them  indis- 
criminately one  for  the  other.  The  point  of  sight  is  also  call- 
ed the  centre  of  the  picture. 

A  visual  ray  is  a  line  from  the  object  to  the  eye.  If  the 
object  is  a  point,  there  is  but  one  visual  ray,  if  it  is  a  line,  the 
visual  rays  form  a  triangle,  if  it  is  a  square,  they  form  a  pyra- 
mid, if  a  circle,  a  cone,  &c.  The  principal  visual  ray  is  that 
from  the  nearest  point  in  the  picture,  or  point  of  sight. 

The  perspective  plane  is  the  surface  on  which  the  picture  is 
delineated  ;  or,  it  is  the  transparent  surface  through  which  we 
suppose  objects  to  be  viewed. 

The  directing  plane  is  a  plane  supposed  to  pass  through  the 
eye  of  the  spectator,  parallel  to  the  perspective  plane. 

The  ground  plane  is  the  earth,  or  the  plane  surface  on 
which  the  spectator  and  objects  are  situated. 

The  horizon,  or  horizontal  plane,  is  one  parallel  to  the  ground 
plane,  and  at  the  height  of  the  spectator's  eye. 

The  horizontal  line  is  the  intersection  of  the  picture  or  per- 
spective plane  with  the  horizontal  plane. 

The  ground  line  is  the  intersection  of  the  perspective  plane 
with  the  ground  plane  ;  or,  it  is  the  line  on  which  the  picture 
is  supposed  to  stand. 

The  perpendicular  is  a  line  on  the  perspective  plane,  drawn 
through  the  point  of  sight,  perpendicular  to  the  ground  line,  and 
horizontal  line. 

The  points  of  distance  are  points  on  the  perspective  plane, 
set  off  from  the  point  of  sight,  sometimes  on  the  horizontal  line, 
and  sometimes  on  the  perpendicular,  at  the  same  distance  from 
the  point  of  sight,  that  the  eye  is  supposed  to  be  at,  from  the 
perspective  plane. 

To  render  the  foregoing  definitions  more  obvious,  a  diagram 
[PI.  II.  Fig.  2.]  is  introduced,  in  which  the  several  planes  are 
supposed  to  be  visible,  and  themselves,  or  a  part  of  each  of 
them,  seen  in  perspective.  X  is  the  eye  of  a  spectator,  or 
point  of  view^  S  T,  the  original  object.  X  T,  and  X  S,  visual 
rays.    X  Y,  the  principal  visual  ray.    A  B  O  P,  the  picture,  or 


ARTS  OF  DESIGNING   AND  PAINTING. 


75 


part  of  the  perspective  plane.  V  W,  the  image  of  the  original 
object  in  the  picture,  or  perspective  plane.  D,  the  point  of  sight, 
or  centre  of  the  picture.  H  N  R  Q,  the  ground  plane.  I  K  Ij 
M,  the  horizon  or  horizontal  plane.  A  B,  the  ground  line,  or 
bottom  of  the  picture.  F  G,  the  horizontal  line.  C  E,  the 
perpendicular.  E,  a  point  of  distance.  Other  points  of  dis- 
tance would  be  at  F  and  G,  if  equally  distant  from  D  with  X 
or  E.    In  Fig.  1,  corresponding  letters  are  used. 

The  vanishing  point  of  the  image  of  a  right  line  is  the  point 
in  which  a  line  parallel  to  it,  passing  through  the  eye,  cuts  the 
perspective  plane.  Lines  which  in  the  original  are  parallel,  in 
the  picture  converge  to  the  same  vanishing  point.  Thus  the 
parallel  railings  of  a  bridge,  or  the  parallel  rows  of  windows  in 
a  building,  all  appear  to  converge  to  the  same  point.  In  PI.  III. 
Fig.  8.  c,  is  the  vanishing  point  of  the  lines  y  x,fk,  and  of  all 
lines  parallel  to  them.  All  hnes  which  are  perpendicular  to  the 
perspective  plane,  have  for  their  vanishing  point  the  centre  of 
the  picture.  Thus  D,  in  PI.  II.  Fig.  1,  is  the  vanishing  point 
of  all  such  lines. 

Plate  IL — A  general  idea  of  the  nature  of  perspective  may 
be  derived  from  the  inspection  of  PI.  II.  fig.  1.  In  adjusting 
this  plate  for  use,  the  folded  or  thick  part  must  be  raised  per- 
pendicularly, the  rest  being  kept  level.  The  part  thus  raised, 
will  represent  the  perspective  plane,  while  the  rest  of  the  plate 
is  the  ground  plane.  The  spectator  is  supposed  to  stand  upon 
Z,  with  his  eye  at  a  height  equal  to  that  of  D,  above  the  ground 
plane.  If  now  the  perpendicular  part  be  supposed  to  be  trans- 
parent, so  that  the  lines  or  objects  beyond,  can  be  seen  through 
it,  the  appearance  which  they  present  on  this  perpendicular 
plane,  will  be  their  true  perspective  representation.  This  may 
be  rendered  obvious,  by  placing  upon  Z,  a  chess  man,  or  any 
other  object,  the  height  of  which  is  equal  to  C  D,  representing 
the  height  of  the  spectator's  eye  from  the  ground  plane.  If 
then  straight  wires  or  threads,  representing  rays,  were  carried 
from  the  top  of  this  object  to  any  of  the  large  letters  upon  the 
black  lines  of  the  ground  plane,  they  would  pass  through  the 


76 


ARTS  OF  DESIGNING   AND  PAINTING. 


perspective  plane  in  the  points  indicated  by  the  ^corresponding 
small  letters.  The  lines  also  which  connect  these  letters,  will 
assume  the  situations  represented  in  the  diagram. 

Problems. — Since  the  figures  of  all  objects  are  contained  within  defi- 
nite lines,  it  is  evident  that  the  whole  art  of  perspective  consists  in  a 
method  of  finding  the  situation  of  all  lines  upon  the  perspective  plane, 
and  of  cutting  those  lines  in  any  given  proportion,  according  to  the 
length  required.  The  same  diagram  [PL  II.  fig.  1.]  will  serve  to  illus- 
trate several  of  the  most  obvious  problems. 

I.  Suppose,  for  instance,  that  it  is  required  to  find  the  perspective 
situation  of  straight  lines,  such  as  H I  and  O  P,  situated  on  the  ground 
plane,  and  parallel  to  the  ground  line.  It  is  first  obvious,  that  if  they 
are  parallel  to  the  ground  line,  they  are  also  parallel  to  one  another, 
and  to  the  picture.  We  then  know  that  the  line  H  I  is  to  be  drawn 
parallel  to  A  B,  and  we  only  require  to  know  at  what  distance  it  must 
be  drawn  from  it.  *  To  ascertain  this,  we  measure  the  perpendicular 
distance  CM,  of  the  given  line  from  the  perspective  plane,  and  set  off 
this  distance  from  C  to  q.  We  then  draw  the  line  G  cutting  the 
line  C  D  in  and  the  line  hi,  drawn  through  m,  parallel  to  the  ground 
line  A  B,  is  the  perspective  situation  of  the  line  H  I,  required. 

The  reason  of  this  will  appear  evident,  from  considering  that  G  be- 
ing situated  at  the  height  of  the  eye  from  the  ground  line  A  B,  and  G 
D  being  equal  to  the  distance  of  the  eye  from  the  perspective  plane ; 
the  line  D  C  may  be  imagined  to  be  the  perspective  plane  seen  edge- 
ways ;  and  then  any  point  5,  situated  at  a  given  distance  beyond  it, 
must  appear  at  m,  in  a  straight  line  drawn  from  the  eye  at  G,  to  it. 
Therefore  m,  is  the  proper  distance  from  C,  at  which  that  point  in  the 
line  required,  must  be  drawn.  In  like  manner,  the  situation  of  the  point 
k,  determining  the  perspective  distance  of  the  line  op,  may  be  found. 

II.  If  it  is  required  to  find  the  perspective  place  of  aline  on  the  ground 
plane  that  is  perpendicular  to  the  ground  line,  we  measure  its  distance 
from  the  perpendicular  C  E,  and  setting  it  off"  from  C  upon  the  ground 
line,  we  draw  a  line  from  the  point,  thus  set  off*,  to  the  point  of  sight 
D,  which  will  give  the  situation  required.  Thus  for  example,  if  we 
wish  to  find  the  perspective  appearance  of  a  line  Q,  D,  which  is  perpen- 
dicular to  the  ground  line  AB,  and  parallel  to  C  D,  we  take  the  distance 
Q,  C,  and  set  it  off*  from  C  to  5,  and  then  D  q  is  the  line  required.  For 

*  Such  lines  are  considered  paraUel  by  writers  on  perspective,  because  a 
line  parallel  to  them  passing  through  the  eye,  can  never  cut  the  perspective 
plane.    Therefore  they  can  have  no  vanishing  point  on  the  perspective  plane. 


ARTS  OF  DESIGNING   AND  PAINTING. 


77 


the  same  reason,  D  r  represents  the  line  D  R ;  also  D  s  represents  D  S, 
and  D  t  represents  D  T.  Since  all  lines  perpendicular  to  the  ground 
line,  when  infinitely  produced,  seem  to  meet  on  the  perspective  plane, 
in  the  point  of  sight  D,  it  is  the  vanishing  point  of  those  lines. 

III.  If  it  is  required  to  find  the  perspective  situation  of  a  line  which 
is  vertical,  i.  e.  perpendicular  to  the  ground  plane,  having  first  ascer- 
tained the  point  upon  which  it  stands  in  the  ground  plane,  we  draw 
from  the  corresponding  point  in  the  perspective  plane,  a  line  perpen- 
dicular to  the  ground  line.  Thus  if  we  have  ascertained  that  the  place 
at  which  a  vertical  line  stands  on  the  ground  plane,  is  at  W,  we  find 
the  corresponding  point  it?,  in  the  perspective  plane,  and  from  it  raise  a 
line  wx,  perpendicular  to  AB,  and  somewhere  in  that  line  continued, 
will  the  required  line  terminate.  The  reason  of  this  will  appear,  when 
we  recollect  that  vertical  lines  are  parallel  to  the  picture,  and  per- 
pendicular to  the  ground  line. 

IV.  If  circles  or  curved  lines  are  to  be  put  in  perspective,  this  may 
be  done  by  describing  squares  about  them,  and  putting  these  in  per- 
spective. This  will  assist  thejudgment  in  completing  the  curved  lines. 
Or  we  may  find  the  perspective  situations  of  a  number  of  points  in  the 
curve,  and  join  these  with  a  steady  hand. 

A  great  number  of  problems,  founded  on  the  principles  of  perspec- 
tive, are  to  be  found  in  works  on  that  science,  and  constitute  an  inter- 
esting study.  But  in  practice,  artists  find  it  convenient  to  resort  to 
some  more  direct  and  compendious  method  of  obtaining  the  perspec- 
tive situation  of  objects,  without  the  trouble  of  mensuration. 

Instrumental  Perspective. — The  rules  usually  laid  down  for 
drawing  in  perspective,  suppose  a  previous  knowledge  of  the 
real  distances,  magnitudes,  and  relative  positions  of  all  the  ob- 
jects that  are  introduced  into  the  picture.  But,  in  many  cases, 
a  person  may  be  so  situated,  that  this  knowledge  cannot  be  ob- 
tained, and  in  many  cases,  likewise,  the  labor,  wliich  this  meth- 
od requires,  is  troublesome  and  discouraging.  Dr  Priestley 
has  described  a  method  of  drawing  objects  in  true  perspective, 
without  moving  from  the  place  in  which  they  are  viewed.  It 
consists  simply  in  taking  observations  of  the  various  points  of 
an  object,  so  as  to  determine  their  elevation  above  the  horizon, 
and  their  declination  from  a  perpendicular. 

To  supply  the  place  of  actual  mensuration,  an  azimuth  quadrant,  or 
a  theoMite,  is  used,  or  any  instrument  by  which  the  elevation  of  an  ob 


t8  ARTS  OF  DESIGNING  AND  PAINTING. 

ject  can  be  found,  and  likewise  its  angle  of  declination  from  the  per- 
pendicular which  goes  through  the  point  of  sight. 

The  artist  having  this  instrument,  and  placing  himself  at  what  dis- 
tance he  thinks  most  convenient,  from  any  objects  that  he  proposes  to 
draw,  lays  down  upon  the  paper  of  his  drawing  board,  two  lines,  cross- 
ing each  other  at  right  angles  ;  one  of  them  F  G,  [PI.  III.  fig.  8.]  to 
represent  the  horizon,  and  the  other  C  E,  the  perpendicular,  passing 
through  the  point  of  sight  D.  He  must  also  choose  any  distance  he 
may  think  proper  to  work  at,  and  set  it  off  from  D  to  E. 

Having  thus  prepared  for  the  operation,  he  pitches  upon  any  point 
in  the  object  in  sight,  as,  for  instance,  that  which  corresponds  to  x ; 
and,  by  the  help  of  the  instrument,  first  of  all,  finds  its  declination  from 
the  perpendicular  to  the  right  or  left  hand.  Supposing  it  to  be  10  de- 
grees to  the  right,  he  sets  off  the  angle  D  E  a,  equal  to  10  degrees,  and 
concludes,  that  the  point  he  wants  to  fix  must  be  somewhere  in  the 
perpendicular  a  e.  To  find  in  what  part  of  this  line  the  point  is,  he 
must  take  its  elevation  above  the  horizon,  and,  supposing  it  to  be  20  de- 
grees, he  makes  a  b  equal  to  a  E,  and  the  angle  ab  x,  equal  to  20  de- 
grees ;  which  finds  x  the  point  required. 

In  this  method  may  the  situation  of  any  other  point  be  found,  and 
these  points,  being  joined  by  lines,  the  whole  object  will  be  delineated. 

But  if  the  objects  to  be  represented,  contain  many  right  lines,  that 
are  parallel  to  each  other,  such  as  occur  in  buildings,  machines,  &c. 
there  will  be  no  occasion  to  take  many  points  ;  because  the  situations 
of  the  lines  may  be  determined  by  vanishing  points,  found  by  the  help 
of  a  few  of  them.  Thus  having  found  y,  in  the  same  manner  as  we 
found  X,  and  knowing  that  the  line  x  y,  is  parallel  to  the  horizon,  we 
produce  it  till  it  touches  the  horizontal  line  in  c,  which  is,  therefore, 
the  vanishing  point  for  that  line,  and  all  that  are  parallel  to  it,  several 
of  which  are  represented  in  the  figure.  The  distance  at  which  these 
parallels  are  drawn,  may  either  be  guessed  by  the  eye,  or  be  determin- 
ed with  more  accuracy  by  finding  a  point  at  one  of  their  extremities, 
in  the  manner  just  described. 

Also,  if  we  know  the  angle  that  any  line,  as  y  z,  makes  with  another 
line,  as  x  y,  the  situation  of  which  is  known,  there  is  no  occasion  to  take 
any  point,  in  order  to  determine  the  direction  of  it.  In  this  figure, 
xy  z  represents  a  right  angle,  which  is  that  which  most  frequently  oc- 
curs in  buildings,  machines,  &c.  To  determine,  therefore,  the  situa- 
tion of  the  line  y  z,  we  consider  that  c,  the  vanishing  point  of  yx,  makes 
the  angle  D  E  c,  equal  to  20  degrees,  the  complement  of  which,  from 
90,  is  70.  We  therefore  make  the  angle  D  E  H  equal  to  70  degrees,  and 
a  line  E  H,  produced  till  it  meets  the  horizontal  line  in  a  place  yithout 


ARTS  OF  DESIGNING   AND  PAINTING. 


79 


the  bounds  of  this  figure,  gives  the  vanishing  point  of  y  z,  and  of  every 
other  hne  parallel  to  it  which  is  at  right  angles  with  the  line  xy.  To 
this  point,  therefore,  we  draw  the  line  y  z,  and  all  the  others  in  that 
plane  that  are  parallel  to  it. 

The  point  x,  is  to  the  right  hand  of  the  perpendicular,  and  it  has  an 
elevation  above  the  horizon ;  but  it  can  require  no  additional  instruc- 
tion, to  be  able  from  this,  to  fix  any  point  to  the  left  hand  of  the  per- 
pendicular, and  one  that  has  a  depression  below  the  horizon. 

If  we  would  introduce  measures  into  a  drawing  made  in  this  manner, 
or  find  a  scale  for  the  picture,  we  measure  some  one  line  in  the  original, 
Siskf.  In  order  to  this,  from  c,  the  vanishing  point  of  the  line  k  /,  we 
take  c  d,  equal  to  c  E,  which  gives  d  the  measuring  point  of  the  line, 
and  from  this  point,  we  draw  two  lines,  one  from  each  extremity  of  the 
line  kf,  to  i  in  the  line  that  bounds  the  picture,  or  any  other  line 
drawn  parallel  to  the  horizontal  line.  Then  we  divide  the  line  ih,  m 
the  same  proportion  as  kf;  and  by  this  means  get  a  scale,  by  which 
we  can  measure  any  other  line  in  the  picture,  or  insert  in  it  other  ob- 
jects of  any  given  magnitudes. 

Mechanical  Perspective. — To  avoid  wholly  the  delay  and 
trouble  of  computation,  artists  frequently  make  use  in  practice, 
of  some  mechanical  method  of  perspective  drawing,  by  which 
the  outlines  of  objects  can  be  obtained  with  expedition,  and 
sufficient  correctness.  Thus  the  camera  ohscura,  and  camera 
lucida,  cast  upon  paper  a  perspective  image,  which  can  be  im- 
mediately traced.  A  method  of  drawing  by  squares  is  like- 
wise easily  practised.  For  this  purpose,  the  paper,  or  surface 
which  is  to  receive  the  picture,  is  divided  by  pencil  lines  into  a 
certain  number  of  squares.  A  small  frame,  of  corresponding 
size,  is  divided  into  a  like  number  of  squares  by  threads,  or  by 
lines  drawn  upon  glass.  This  frame  is  placed  perpendicularly 
between  the  eye  and  the  object,  and  kept  at  a  stationary  distance 
from  the  eye,  which  is  also  fixed.  The  outlines  and  parts  of 
objects  which  appear  in  particular  squares  of  the  frame,  are 
transferred  to  corresponding  ones  on  the  paper,  and  in  this  way 
the  principal  points  of  the  perspective  view  may  be  obtained. 

Perspectographs. — Various  instruments  have  been  invented 
under  the  name  perspectographs,  to  be  used  in  obtaining  the 
points  and  outlines  of  original  objects.    They  commonly  con- 


80 


ARTS  OF  DESIGNING   AND  PAINTING. 


sist  of  a  fixed  part  .perforated  with  a  small  hole  in  the  point  of 
view,  and  a  moveable  part  situated  in  the  perspective  plane, 
and  capable  of  traversing  any  part  of  it.  This  moveable  part 
may  consist  of  any  minute  substance,  or  which  is  better,  a 
moveable  point  may  be  obtained  by  the  intersection  of  two 
threads.  Any  points  in  the  perspective  plane  may  thus  be 
found,  and  transferred  to  the  picture  by  bringing  the  part  of  the 
instrument  which  contains  them,  into  contact  with  the  paper. 

A  simple  and  very  useful  perspectograph  may  be  made  by 
erecting  a  pane  of  glass  upon  one  end  of  a  board,  or  short  ta- 
ble, and  a  moveable  piece  with  an  aperture  for  the  eye  at  the 
other  end".  *  The  moveable  piece  is  to  be  fixed  at  any  conve- 
nient distance,  and  the  object  is  to  be  viewed  from  it,  through 
the  pane  of  glass.  The  outlines,  as  they  appear,  are  traced 
upon  the  glass  with  a  stick  of  w  ax  sharpened  like  a  crayon,  and 
they  may  be  afterwards  rendered  very  plain,  and  transferable, 
by  sprinkling  them  with  any  black  powder. 

The  geometrical  and  mechanical  methods  w^hich  have  been 
described,  will  enable  a  person  not  previously  conversant  with 
the  art,  to  obtain  correct  perspective  representations  of  any  ob- 
ject. But  by  long  practice,  in  drawing  from  nature,  a  certain 
tact  is  acquired  by  painters,  which  enables  them  by  the  accura- 
cy of  the  eye  and  judgment  alone,  to  make  correct  views  of 
objects,  without  the  aid  of  any  computation  or  mechanical  pro- 
cess. Thus  rainature  painters  produce  the  nicest  resemblance 
of  the  human  countenance,  in  any  position,  with  no  other  guide, 
than  the  faculty  obtained  by  experience,  of  estimating  the  ex- 
act shape  and  proportion,  which  each  part  of  the  original  should 
bear  upon  the  picture. 

Projections. — The  projections  of  a  body,  are  the  different 
modes  by  which  it  may  be  delineated  on  a  plane  surface.  That 
which  has  already  been  described,  is  called  the  scenographic 
projection,  and  represents  objects  as  they  actually  appear  to  the 

*  No  method  fixes  the  eye  so  eflfectually,  as  to  rest  the  teeth  upon  a  solid, 
or  fixed  body. 


ARTS  OF  DESIGNING   AND  PAINTING. 


81 


eye,  at  limited  distances.  The  orthographic  projection  repre- 
sents objects  as  they  would  appear  to  the  eye  at  an  infinite  dis 
tance,  the  rays  which  proceed  from  them,  being  parallel,  instead 
of  converging.  The  shadow,  which  a  body  casts  in  the  rays 
of  the  sun,  may  be  considered  as  an  orthographic  projection. 
In  this  projection,  lines  which  are  parallel  in  the  original,  are 
parallel  in  the  picture,  and  do  not  converge  to  any  vanishing 
point.  Their  comparative  length,  also,  is  not  affected  by  dif- 
ference of  apparent  distance.  The  orthographic  projection  is 
much  used  in  delineating  buildings,  machinery,  &z;c.,  because 
those  parts  of  the  dravving  which  are  not  foreshortened,  main- 
tain their  true  relative  size,  so  that  measures  can  be  taken  from 
them.  In  PL  III.  Fig.  7,  No.  1  is  the  scenographic,  and  No  2, 
the  orthographic  projection  of  a  cube.  In  addition  to  these, 
the  term  ichnographic  projection,  is  sometimes  used  to  express 
the  horizontal  delineation,  or  ground  plan  of  an  object.  A 
birds'  eye  view  is  a  scenographic  or  orthographic  projection,  ta- 
ken from  an  elevated  point  in  the  air,  from  which  the  eye  is 
supposed  to  look  down  upon  the  objects. 

Isometrical  Perspective. — This  name  has  been  introduced  by 
Professor  Farrish,  to  express  a  kind  of  drawing  peculiarly  con- 
venient in  delineations  of  machinery,  and  bodies  of  regular  fig- 
ure. It  is  a  species  of  orthographic  projection,  in  which  three 
planes,  at  right  angles  with  each  other,  appear  similar  and  equal. 
An  idea  of  it  may  be  formed,  by  supposing  a  cube  to  be  so 
placed,  that  one  of  its  angles  will  appear  in  the  centre,  while  its 
outline  will  be  a  true  hexagon.  In  this  projection,  the  sides  of 
the  cube  appear  equal,  and  all  sections  of  the  cube  parallel  to 
either  side,  will  also  be  equal.  All  right  angles  are  represent- 
ed by  angles  of  60  degrees,  or  the  supplement  of  60  degrees. 
All  circles  parallel  to  either  of  the  three  planes,  will  be  repre- 
sented by  similar  ellipses.  Figures  not  parallel  to  either  of  the 
planes,  may  be  calculated  by  easy  rules.  It  is  therefore  the 
easiest  and  most  expressive  kind  of  drawing  for  the  wheelwork, 
axlesj  and  regular  frames  of  machinery ;  for  philosophical  in- 
11 


82 


ARTS  OF  DESIGNING  AND  PAINTING. 


stniments,  and  for  many  architectural  designs.  *  In  PI.  III.  fig. 
9,  is  an  isometrical  view  of  a  cube,  with  circles  inscribed  on  its 
sides,  and  the  axes  of  those  circles  projecting  a  short  way. 

CHIARO  OSCURO. 

Next  to  correct  perspective,  the  most  important  circumstance 
in  painting,  is  the  correct  distribution  of  light  and  shade.  To 
the  skilful  management  of  these,  we  are  indebted  for  the  strength 
and  liveliness  of  pictures,  and  what  is  technically  called  their 
relief,  or  the  elevation  which  certain  parts  appear  to  assume 
above  the  plane  upon  which  the  picture  is  made. 

Light  and  Shade. — Light  and  shade,  as  they  appear  to  us 
upon  natural  objects,  are  the  consequences  of  the  rectilinear 
motion  of  the  rays  cast  upon  them  by  luminous  bodies.  If  an 
object  be  exposed  to  the  rays  of  the  sun,  or  of  a  single  lamp 
or  candle,  those  parts  or  surfaces  which  are  presented  directly 
to  these  rays,  become  strongly  illuminated,  and  acquire  a  lighter 
cast  approaching  to  white.  Those  surfaces  which  stand  ob- 
liquely to  the  light,  receive  less  of  the  rays,  and  of  course  have 
a  deeper  tinge.  Those  lastly,  which  are  averted  from  the  light, 
and  receive  no  rays  but  such  as  are  reflected  to  them  from  oth- 
er objects,  acquire  a  very  dark  shade,  approaching,  when  con- 
trasted with  the  others,  towards  black. 

The  distribution  of  light  and  shade  upon  any  object,  is  always 
proportionate  and  correspondent  to  its  shape.  An  even  or 
plane  surface,  exposed  to  the  sun's  rays,  will  be  equally  illumi- 
nated throughout,  since  whatever  be  its  position,  hs  parts  will 
all  make  a  similar  angle  with  ihe  rays.  But  uneven  or  irregu- 
lar surfaces  will  be  unequally  illuminated,  the  prominent  parts 
receiving  most  light,  and  the  depressed  portions  most  shade,  an 
effect  which  will  be  increased,  if  the  light  falls  obliquely  or 
sideways.    If  the  irregularities  of  surface  be  sharp  and  strong, 

*  For  the  principles  of  isometrical  drawing,  see  the  Cambridge  Philosophi- 
cal Transactions ;  or  Gregory's  Mathematics  for  Practical  Men,  p.  179. 


ARTS  OF  DESIGNING   AND  PAINTING. 


83 


the  changes  from  light  to  shade,  will  be  sudden,  and  the  con- 
trast great.    On  the  other  hand,  if  they  are  smooth  and  round 
ed,  the  transition  will  be  soft  and  gradual. 

Association. — As  bodies  are  never  seen,  except  when  they 
are  illuminated,  the  manner  in  which  light  and  shade  are  distrib- 
uted upon  them,  forms  by  association  a  part  of  our  ideas  of 
their  shape.  Painters  have  learned  to  imitate  this  arrangement 
of  light  and  shade,  by  varying  the  quantity  and  intensity  of 
their  coloring  substances,  so  as  to  produce  in  the  mind  the  same 
associations  of  shape  from  a  plane  surface,  as  would  arise  from 
the  faUing  of  light  on  the  original  object  itself.  This  art  con- 
stitutes what  is  technically  called  the  chiaro  oscuro,  from  the 
Italian  words  signifying  dear  and  obscure.  Next  to  perspective 
it  is  the  most  important  part  of  painting,  and  there  are  many 
cases  in  which  perspective  alone  would  wholly  fail  to  convey  to 
us  a  correct  idea  of  the  form  of  objects,  were  it  not  assisted  by 
appropriate  insertion  of  lights  and  shades.  Thus  a  circle,  a 
sphere,  and  a  cone  viewed  vertically,  may  all  have  the  same 
perspective  outline ;  but  their  difference  of  figure  becomes  ap- 
parent, as  soon  as  we  consider  their  distribution  of  light  and 
shade. 

Direction  of  Light. — The  most  distinct  perceptions  of  shape 
are  produced  when  the  hght  falls  in  one  direction,  e.  g.  when 
it  is  received  immediately  from  the  sun,  or  from  a  single  win- 
dow or  candle.  The  distinctness  of  an  object  is  always  im- 
paired, when  it  is  situated  between  cross  hghts,  or  when  it  is  il- 
luminated by  a  variety  of  windows  or  candles  on  different  sides 
of  the  room.  An  object  may  even  be  so  surrounded  with  lights, 
that  it  shall  be  impossible  to  discover  its  exact  shape.  Its  out- 
line indeed  will  be  discernable,  but  the  equal  illumination  on 
all  sides,  will  exclude  the  existence  of  shadow,  and  of  course 
we  shall  lose  the  power  of  appreciating  the  comparative  dis- 
tance of  its  parts  from  the  eye.  In  most  paintings,  we  find 
that  the  principal  mass  of  light  falls  in  one  direction.  An  ob- 
lique or  a  sideway  direction,  is  most  common,  though  a  front, 
and  even  a  back  light,  is  managed  to  produce  very  striking 


84 


ARTS  OF  DESIGNING   AND  PAINTING. 


effects.  Painters  also  exercise  their  skill  with  the  introduction 
of  cross  lights,  from  different  windows,  or  lamps  ;  but  the  suc- 
cessful execution  of  a  piece  of  this  sort  is  more  difficult,  than 
with  a  single  light. 

Reflected  Light. — Owing  to  the  reflection  which  takes  place 
from  all  terrestrial  bodies,  we  find  that  objects,  in  most  situations, 
have  not  only  a  principal  or  direct  light,  but  also  a  secondary 
or  reflected  one.  Hence  the  darkest  part  of  globular  and  cy- 
lindrical bodies,  is  not  that  which  is  most  remote  from  the  orig- 
inal light.  This  part  receives  from  the  reflection  of  objects 
beyond  it,  a  faint  illumination,  so  that  the  darkest  part  will  be 
found  between  it  and  the  part  on  which  the  light  directly  falls. 
See  the  sphere  represented  PI.  III.  Fig.  4. 

Sharp  lights,  or  such  as  are  intense  and  sudden,  indicate  pol- 
ished surfaces,  and  are  employed  to  represent  them.  Where 
they  are  accompanied  by  very  deep  shades,  they  express  great 
elevation  above  the  common  surface.  Faint  lights,  on  the 
contrary,  imply  a  dull  surface,  obscure  illumination,  or  small 
elevation. 

Expression  of  Shape. — Light  and  shade,  are  not  adequate,  in 
all  cases,  to  give  us  certain  indications  of  the  forms  of  bodies. 
Surfaces  which  appear  concave  in  one  direction  of  the  light, 
may  appear  convex,  if  the  light  is  introduced  from  the  opposite 
side.  In  contemplating  an  undulating  object,  like  a  curtain,  or 
its  picture  upon  paper  hangings,  we  are  often  at  a  loss  to  dis- 
tinguish the  elevated,  from  the  depressed  portions;  and  by  a 
little  effort  of  the  imagination,  we  can  persuade  ourselves  that 
a  particular  part  is  at  one  time  elevated,  and  at  another,  de- 
pressed. Cameos  and  intaglios  maybe  mistaken  for  each  oth- 
er, and  any  of  the  figures  [PI.  III.  fig.  4.]  may  appear  promi- 
nent or  depressed,  in  the  same  part,  by  reversing  the  direction 
in  which  the  light  is  supposed  to  strike  upon  them. 

In  cases  of  this  sort,  our  final  ideas  of  shape  are  derived, 
not  only  from  the  object  itself,  but  from  its  relations  with  con- 
tiguous objects. 


ARTS  OF  DESIGNING   AND  PAINTING. 


86 


Eyes  of  a  Portrait. — The  influence  which  the  association  of 
contiguous  objects  has  upon  our  ideas,  is  strikingly  exemplified  in 
the  eyes  of  a  portrait.  We  estimate  the  direction  of  the  eyes, 
not  only  from  the  position  of  the  ball  in  regard  to  the  eyelids, 
but  also  from  the  relative  position  of  the  remaining  features  of 
the  face.  Dr  Wollaston  has  shown,  that  the  same  eyes  in  a 
picture,  which  looks  at  us,  may  be  made  to  appear  averted  from 
us,  if  we  apply  new  features  to  the  lower  half  of  the  face. 
[PI.  III.  Fig.  3.]  The  reason,  why  the  eyes  of  a  portrait  ap ; 
pear  to  follow  us,  in  all  parts  of  the  room,  is  simply,  that  the 
relative  position  of  the  features  cannot  change,  so  that  if  the 
picture  appears  to  look  at  us  once,  it  must  appear  to  look  at  us 
always.  If  we  move  to  one  side  of  a  portrait,  the  change, 
which  happens,  is  unlike  that  which  would  take  place  in  a  bust, 
or  living  face.  The  picture  is  merely  foreshortened,  so  that  we 
see  a  narrower  image  of  a  face,  but  it  is  still  that  of  a  face  look- 
ing at  us.  And  if  the  canvass  be  transparent,  the  same  effect 
takes  place  from  the  back  of  the  picture. 

Shadows. — Shadows  are  cast  in  the  direction  opposite  to  that 
by  which  we  suppose  the  light  to  enter,  and  their  introduction 
in  pictures,  always  heightens  the  effect.  A  painted  object,  is 
relieved,  or  raised  from  the  surface,  by  the  expression  of  light 
and  shade  on  itself.  But  the  relief  is  greatly  increased,  if  the 
shadow  which  it  makes  on  the  ground,  or  other  surface,  be  also 
introduced.  Shadows  are  commonly  softened  off  at  the  edges, 
or  terminate  gradually.  When,  however,  the  light  is  strong,  or 
the  shadow  very  near  to  the  object,  its  termination  is  more 
abrupt. 

Aerial  Perspective. — This  name  is  given  by  painters,  to  the 
mode  of  producing  the  effect  of  distance,  by  a  diminution  in 
the  distinctness  and  brightness  of  objects,  according  to  their 
remoteness  from  the  eye,  and  the  condition  of  the  medium 
through  which  they  are  seen.  It  is  well  known,  that  distant 
objects  appear  indistinct,  and  of  a  greyish  or  bluish  tinge,  from 
the  effect  produced  by  the  intervening  atmosphere.  Their  in- 
distinctness is  increased,  if  the  atmosphere  is  hazy.    Their  ap- 


86 


ARTS  OF  DESIGNING  AND  PAINTING. 


pearance  is  also  modified  by  the  degree  of  their  illumination, 
and  by  the  character  of  the  light  which  falls  on  them.  The 
painter,  therefore,  finds  it  necessary  to  consider  the  depth  of 
atmosphere  which  is  interposed  between  him  and  his  object, 
the  condition  of  this  atmosphere,  and  the  quantity  and  color  of 
the  light  which  falls  on  it,  and  on  the  objects.  A  want  of  at- 
tention to  these  circumstances,  gives  rise  to  the  defect  called 
hardness  in  painting. 

COLORING. 

By  the  aid  of  perspective,  and  the  chiaro  oscuro  alone,  very 
good  representations  of  objects  may  be  obtained.  All  our  com- 
mon engravings,  wood  cuts,  drawings  in  Indian  ink,  in  black 
crayons,  &;c.,  derive  their  expressiveness  from  these  only.  But 
a  still  nearer  approach  to  the  appearance  of  nature,  is  made,  by 
the  employment  of  colors  analogous  to  those  which  are  found 
to  exist  in  the  objects  represented. 

Colors. — From  the  science  of  optics,  we  learn  that  the  solar 
*  beam  is  divisible  into  seven  primary  colors,  white  being  the  mix- 
ture, and  black  the  privation  of  all  of  them.  These  colors, 
are  violet,  indigo,  blue,  green,  yellow,  orange,  red.*  Three  of 
these  are  capable  of  producing  all  the  rest,  by  their  intermixture 
and  degree,  viz.  blue,  red,  and  yellow. 

The  color  belonging  to  different  natural  objects,  was  suppos- 
ed, by  Newton,  to  be  occasioned  by  a  power  w^hich  their  sur- 
faces possess,  to  reflect  certain  rays,  while  they  absorb  all  the 
rest.  This  power  is  so  infinitely  diversified  in  nature,  that  we 
find  not  only  every  kind  of  primary  ray  reflected,  but  likewise 
every  possible  tint,  and  intermediate  grade,  which  can  be  pro- 
duced by  the  admixture  of  two  or  more  original  colors.  To 

*  Dr  Wollaston  found  the  spectrum  formed  in  looking  through  a  prism  at  a 
narrow  line  of  light,  to  consist  of  four  colors,  red,  green,  blue,  and  violet,  with 
a  narrow  stripe  of  yellow.  The  three  simple  colors,  red,  green,  and  violet, 
may  produce  yellow,  by  the  admixture  of  red  and  green ;  crimson,  by  red  and 
violet;  blue,  by  green  and  violet,  and  white  by  the  combination  of  all  three. 


ARTS  OF  DESIGNING  A.ND  PAINTING. 


87 


represent  these  various  hues,  it  is  necessary  that  the  painter 
should  possess  coloring  substances  analogous  to  them  all,  or 
capable  of  producing  them  all  by  mixture,  and  that  he  should 
apply  them  in  sucli  a  manner,  that  the  true  color  may  remain 
distinct,  independently  of  the  lights  and  shades  necessary  to 
place  the  objects  in  relief. 

Shades. — In  a  colored  painting  of  an  object  which  has  any 
rotundity  of  form,  there  are  usually,  at  least,  three  tints,  or  de- 
grees of  color.  These  are  the  light,  the  middle  tint,  and  the 
shade.  Of  these,  the  middle  tint  is  the  one  which  represents 
the  true  color  of  the  object,  and  occupies  an  intermediate  situ- 
ation between  the  light  and  shade.  Thus  in  the  painting  of  a 
red  fruit,  for  instance  the  cherry,  the  middle  tint  is  vermillion, 
or  some  similar  color,  being  that  which  the  surface  of  the  fruit 
would  have,  if  it  were  perfectly  flat.  The  part  of  the  fruit 
nearest  the  light,  has  a  very  bright  color  partaking  of  white, 
while  the  remote  parts  are  shaded  with  lake  or  some  darker 
red.  In  like  manner,  a  yellow  fruit,  like  the  lemon,  has  not 
only  the  true  color  of  the  rind,  but  is  lightened  at  the  top  with 
straw  color  or  white,  and  shaded  with  brown  toward  the  edges. 
It  is  necessary  that  the  colors  used  for  dark  shading,  should  be 
in  some  degree  correspondent  with  the  middle  tint,  and  not  di- 
ametrically opposite  to  it.  Thus,  in  single  objects,  yellow 
cannot  be  shaded  with  blue,  nor  red  with  green. 

Tone. — Pictures  differ  from  each  other  in  the  respective 
depth  of  color,  which  pervades  the  whole  piece.  The  word 
tone,  borrowed  from  the  art  of  music,  signifies  in  painting,  the 
peculiar  cast,  or  governing  hue,  which  a  picture,  or  a  color, 
possesses.  Thus  if  dark  masses  of  color,  with  feeble  lights, 
predominate,  the  piece  has  a  deep  or  low  tone,  while  if  the 
reverse  exists,  a  bright  or  light  tone  is  produced.  It  is  essen- 
tial to  harmony  that  a  picture  should  have  the  same  tone 
throughout,  or  that  its  lights  and  shades  should  correspond  in 
their  intensity  to  the  tone  which  governs  the  whole. 

Harmony. — When  different  objects  are  grouped  together  in 
the  same  view,  each  one  possesses  two  kinds  of  color,  the  orig- 


88 


ARTS  OF  DESIGNING  AND  PAINTING. 


inal  color,  and  the  adventitiovs.  The  original  color,  often  called 
among  painters  the  local  color,  is  that  which  belongs  to  the  object 
itself,  independent  of  situation.  The  adventitious  color,  is  that 
which  is  reflected  upon  it  from  neighboring  objects,  and  which 
of  course  depends  upon  situation.  For  example,  the  color  of 
the  human  face  is  that  which  we  call  flesh  color,  and,  if  painted 
alone,  may  be  represented  by  the  shades  of  that  color.  If, 
however,  it  is  surrounded  by  a  purple  drapery,  it  receives  a 
purplish  tinge,  and  requires  to  he  so  represented.  In  like  man- 
ner, a  yellow  dress  communicates  to  it  a  yellowish  cast,  &c. 
An  attention  to  this  adventitious  coloring,  combined  with  a  uni- 
formity of  tone,  constitutes  the  basis  of  what  is  technically  called 
harmony  in  painting.  Harmony  requires  that  strong  and  glaring 
colors  should  never  be  forcibly  contrasted  with  each  other,  but 
that  each  object  should  partake  at  its  edges  of  a  certain  portion 
of  the  color  which  predominates  in  objects  near  to  it.  This 
rule  not  only  produces  effects  most  grateful  to  the  eye,  but  an 
observance  of  it  gives,  in  fact,  the  only  true  representation  of 
nature. 

Contrast. — Colors  are  divided  by  painters,  into  the  warm  and 
the  cold.  Warm  colors  are  those  in  which  red  and  yellow  pre- 
dominate. Cold  colors  are  blue,  grey,  and  others  allied  to 
them.  Neutral  colors  are  intermediate  tints,  or  mixtures.  Of 
the  various  pigments  or  coloring  substances,  which  painters  em- 
ploy,  none  have  the  genuine  brilliancy  of  the  prismatic  rays ; 
and  all  fall  short  of  the  hues  produced  by  nature  in  living  ob- 
jects. The  petal  of  a  flower,  the  feather  of  a  bird,  and  the 
wing  of  an  insect,  are  tinged  with  a  richness  and  splendor, 
which  no  factitious  colors  can  equal.  Painters  can  only  ap- 
proach, when  necessary,  towards  the  brightness  of  natural  col- 
ors, by  availing  themselves  of  the  efl^eci  of  contrast,  and  by 
heightening  one  color  by  the  introduction  of  others,  which  pre- 
pare the  eye  for  its  more  perfect  and  favorable  reception. 

Remarks. — The  power  of  giving  true  representations  of  ob- 
jects, is  derived,  originally,  from  an  attentive  study  of  the  colors 
and  appearance  which  they  actually  exhibit  in  nature  ;  after- 


ARTS  OF  DESIGNING  AND  PAINTING. 


89 


wards  from  a  comparison  of  the  success  of  different  artists,  and 
an  attention  to  the  means  they  have  employed.  What  helongs 
to  the  philosophical  part  of  painting,  can  hardly  be  said  to  extend 
beyond  the  correct  imitation  of  nature.  But  the  inventive  part, 
the  design  and  composition  of  great  pieces,  such  as  have  not 
necessarily  any  originals  in  nature,  requires  not  only  philosophic 
accuracy,  and  practical  skill,  but  also  demands  original  genius, 
strength  and  fertility  of  imagination,  and  a  strong  perception  of 
sublimity  and  beauty,  whether  natural  or  moral.  To  paint  a 
portrait,  or  a  landscape  from  nature,  requires  no  more  than  a 
faculty  of  correct  imitation.  But  to  express  on  the  canvass  a 
scene  of  history  or  of  fiction,  to  create  forms  of  ideal  beauty 
exceeding  the  realities  of  life,  and  to  express,  by  attitudes  and 
lineaments,  passions,  which  tell  the  events  they  accompa- 
ny,— this  excellence  is  attained  by  few  ;  it  is  not  to  be  taught  by 
any  rules  of  art,  but,  hke  poetry,  and  eloquence,  it  is  within  the 
reach  of  those  only,  whom  a  strong  and  exclusive  interest  in  the 
pursuit,  has  qualified  to  feel  deeply,  and  to  express  powerfully. 

JVote. — For  the  modes  of  painting  in  water,  oil,  fresco,  Stc, 
also  for  coloring  substances,  see  Chapter  XVIII. 


Malton's  Treatise  on  Perspective,  fol.  1779; — Priestley's  In- 
troduction to  Perspective,  8vo.  1770; — Wood's  Lectures  on  Perspec- 
tive, with  an  Apparatus,  1809; — Blunt's  Essay  on  Mechanical  Draw- 
ing, 4to.  1811 ; — Lucas's  Progressive  Drawing  Book,  Baltimore, 
1827  ; — Burnet,  on  Light  and  Shade,  4to.  1827; — Burnet,  on  Color- 
ing, 4to.  1827  ; — Vallee,  Traite  de  la  Science  du  Dessin,  4to.  Paris, 
1821 ; — MiLLiN,  Dictionnaire  de  Beaux  Arts,  3  torn.  8vo.  1806 ; — El- 
WEs's  Dictionary  of  Fine  Arts,8vo.  1826; — Works  of  Sir  J.  Reynolds, 
—Opie,—Fuseli,— Barry, — West,— De  Piles,  &c.  &c. 


CHAPTER  V. 


ARTS  OF  ENGRAVING  AND  LITHOGRAPHY. 

The  arts  of  engraving  and  lithography,  bear  the  same  rela- 
tion to  drawing,  that  the  art  of  printing  does  to  that  of  writing ; 
the  first  being  intended  for  the  expression  of  original  designs, 
the  latter  for  the  multiplication  of  copies  of  the  design,  when 
made. 

ENGRAVING. 

Origin. — The  origin  of  copperplate  engraving,  appears  to 
have  been  in  the  fifteenth  century,  previously  to  which  time  it 
was  probably  unknown.  The  first  inventors  of  engraving,  were 
the  goldsmiths,  who,  from  the  habit  of  marking  ciphers  and  lit- 
tle devices  on  their  wares,  acquired  a  dexterity  and  despatch  in 
the  use  of  the  graving  tool,  and  at  the  same  time,  a  power  of 
producing  subjects  of  such  neatness  and  delicacy,  that  a  desire 
was  naturally  excited  in  them,  to  preserve  and  increase  the  pro- 
ducts of  the  art,  by  transfering  them  to  paper.  This  object 
was  effected  by  the  use  of  a  suitable  pigment,  and  the  aid  of 
the  rolling  press. 

Materials. — Common  engraving  differs  from  printing,  in  hav- 
ing its  subjects  or  devices  cut  into,  or  below,  the  surface  of  a 
metallic  plate,  instead  of  being  elevated  or  raised  above  it,  as 
in  types,  and  wood  cuts.  For  the  purpose  of  engraving,  a  va- 
riety of  metals  have  been  employed,  and  various  combinations 
or  alloys.  Copper  has,  however,  been  selected  by  common 
consent,  as  uniting  the  greatest  number  of  desirable  qualities  ; 
having  sufficient  softness  to  permit  it  to  be  cut  w^hen  cold,  and 
sulBcient  hardness  and  tenacity,  to  resist  the  action  of  the  press. 


ARTS   OF  ENGRAVING  AND  LITHOGRAPHY. 


91 


and  the  wearing  of  continued  friction.  A  plate  of  the  best 
copper  is  selected,  about  one  fourth  of  an  inch  thick,  having  one 
side  finely  pohshed,  and  its  edges  rounded,  to  prevent  it  from  cut- 
ting the  paper.  The  engraver  works  opposite  to  a  window,  hav- 
ing a  screen  interposed  to  soften  the  light,  and  the  plate  placed  on 
an  oblique  table  in  the  most  convenient  position  for  seeing. 

Instruments. — The  instruments  employed  in  the  practice  of 
the  art,  are  the  following.  1.  The  graver.  This  is  a  small 
steel  bar,  of  a  prismatic  form,  having  one  end  attached  to  an 
oblique  handle,  and  the  other  ground  off  obliquely,  so  as  to 
produce  a  sharp  point  at  one  angle.  In  working,  this  instru- 
ment is  held  in  the  palm  of  the  hand,  and  pushed  forward,  so 
as  to  cut  out  a  portion  of  the  copper.  2.  The  dry  point. 
This  is  a  strong  bluntish  needle,  fixed  in  a  handle,  and  intend- 
ed for  drawing  the  finer  lines.  It  is  held  in  the  fingers,  in  the 
same  way  as  a  pen  or  pencil.  3.  The  scraper^  a  triangular 
instrument,  with  concave  sides,  and  sharp  edges,  intended  for 
removing  or  scraping  off  portions,  which  are  accidentally  raised 
above  the  surface.  4.  The  burnisher.  This  is  merely  a  blunt 
smooth  tool,  for  rubbing  out  blemishes,  and  smoothing  the  sur- 
face of  the  copper.  Various  kinds  of  varnish,  rosin,  wax, 
.  charcoal,  and  mineral  acids,  are  also  employed  in  different  parts 
of  the  operation,  according  to  the  subject  and  the  style  of  en- 
graving which  is  adopted. 

Styles. — The  principal  varieties,  or  styles,  of  engraving  on 
copper,  are  the  following.  1.  Line  engraving.  2.  Stippling. 
3.  Etching.  4.  Mezzo  tinto.  5.  Aqua  tinta.  Lithography, 
and  some  other  modes  of  multiplying  designs,  are  imitations 
and  substitutes,  rather  than  species  of  engraving.  * 

Line  Engraving. — Line  engraving,  called  by  the  French, 
Gravure  en  taille  douce,  is  one  of  the  most  common  species  of 
engraving ;  and  though  less  elaborate  than  the  second  mode, 

'  Musical  characters  are  sometimes  executed  in  a  mode  different  from  all 
these,  by  making  impressions  with  a  punch  upon  pewter,  or  some  other  soft 
metal. 


AJITS  OF  ENGRAVING  AND  LITHOGRAPHY. 


lias  produced  most  of  the  finest  and  boldest  specimens  of  the 
art.  In  this  species,  the  surfaces  and  figures,  the  lights  and 
shades,  are  produced  by  the  multiplication  of  minute  lines,  cut 
in  by  the  graver  and  dry  point,  approaching  each  other  so  near- 
ly, that  the  inequality  produced  by  the  admixture  of  black  and 
white,  does  not  offend  the  eye,  nor  interrupt  the  harmony  of 
the  piece.  The  effect  and  beauty  of  hne  engravings,  depends 
much  upon  the  smoothness  of  the  lines,  their  gradual  swell  and 
decrease,  and  their  evenness  or  parallel  situation. 

For  engraving  in  this  manner,  the  artist  transfers  the  outlines 
of  his  original  drawing,  by  tracing  them  with  black  lead,  on  an 
oiled  paper,*  and  afterwards  passing  this  paper  through  the 
press  in  contact  with  the  copperplate,  which  is  previously 
covered  with  a  thin  coating  of  wax.  A  sufficient  quantity 
of  the  lead  adheres  to  the  copper,  to  enable  him  to  engrave 
the  outhnes  with  great  accuracy.  The  graver  is  then  held  in 
the  palm  of  the  hand,  and  pushed  forward  with  a  strong  but 
steady  and  regular  motion  until  a  line  is  completed.  The  gra- 
ver by  its  operation,  removes  a  thread  of  copper  from  the  line, 
and  at  the  same  time  raises  the  surface  on  each  side  of  it,  form- 
ing what  is  called  a  hurr.  This  burr  is  subsequently  removed 
by  the  process  of  scraping  and  burnishing.  After  the  outlines 
are  finished,  the  dark  surfaces  are  introduced  by  means  of  close 
parallel  lines  cut  in,  in  the  same  manner  as  before.  Gradations 
of  light  and  shade  are  produced  by  the  gradual  and  simultane- 
ous tapering  of  all  the  lines  which  constitute  the  dark  portions, 
and  the  softness  and  regularity  with  which  this  is  accomplished, 
greatly  affects  the  beauty  of  the  piece.  Very  dark  shades  are 
produced  by  lines  crossing  each  other,  either  in  squares  or  lo- 
zenges, which  are  varied  according  to  the  nature  of  the  subject. 
Very  light  shades,  on  the  contrary,  are  left  untouched,  or  cov- 

*  Paper  rendered  transparent  with  spermaceti,  is  useful  in  tracing  figures 
with  a  lead  pencil.  If  paper  be  varnished  with  a  mixture  of  Canada  balsam, 
and  oil  of  turpentine,  very  distinct  lines  may  be  traced  on  it  with  the  dry 
point  only,  and  these  may  be  again  transferred,  by  varnishing  the  copper,  and 
tracing  them  upon  it,  through  the  paper.  This  method  is  now  much  employ- 
ed by  engravers. 


ARTS   OF  ENGRAVING  AND  LITHOGRAPHY. 


03 


ered  with  broken  lines.  Lines  which  swell  or  taper,  are  first 
cut  of  a  uniform  size,  and  afterwards  deepened  by  a  second  or 
third  stroke  of  the  graver.  Mistakes  or  blemishes,  are  erased 
from  the  plate,  either  by  burnishing,  with  the  proper  instrument, 
or  by  rubbing  with  charcoal. 

Stippling. — The  second  mode  of  engraving,  is  that  called 
stippling,  or  engraving  in  dots.  This  resembles  the  last  men- 
tioned method  in  its  processes,  except  that  instead  of  lines,  it  is 
finished  by  minute  points  or  excavations  in  the  copper.  These 
punctures  when  made  with  the  dry  point,  are  circular,  when 
made  with  the  graver,  they  are  rhomboid al  or  triangular.  The 
variations  and  progressive  magnitude  of  these  dots,  give  the 
whole  effect  to  stippled  engraving.  This  style  of  work,  is  al- 
ways more  slow,  laborious,  and  of  course  more  expensive,  than 
engraving  in  lines.  It  has,  however,  some  advantages  in  the 
softness  and  delicacy  of  its  lights  and  shades,  and  approaches 
nearer  to  the  effect  of  painting,  than  the  preceding  method.  A 
more  expeditious  way  of  multiplying  the  dots,  has  been  contriv- 
ed in  the  instrument  called  a  roulette,  a  toothed  wheel,  fixed  to 
a  handle,  which  by  being  rolled  forcibly  along  the  copper  pro- 
duces a  row  of  indentations.  This  method,  however,  is  less 
manageable  than  the  other,  and  generally  produces  a  stiff 
effect. 

Etching. — Etching  is  the  third  mode  of  engraving,  and  is 
performed  by  chemical  corrosion.  It  is  apparently  the  easiest 
mode  of  engraving,  requiring  least  practice  in  the  operator.  In 
fact,  any  person  who  can  draw,  may  etch  coarse  designs  toler- 
ably well,  after  having  acquainted  himself  with  the  theory  only. 
Hence  we  find  that  engineers,  naturalists,  surgeons,  &;c.  some- 
times etch  their  own  plates,  especially  of  light  subjects. 

A  plate  for  etching,  is  prepared  in  the  same  manner  as  for 
common  engraving.  It  is  then  covered  throughout  its  whole 
surface,  with  a  very  thin  coating  of  varnish  made  of  wax,  mas- 
tic, and  asphaltum  ;  sometimes  of  rosin,  and  animal  oil,  or  of 
linseed  oil  inspissated  by  boiling.  This  varnish  is  black- 
ened by  the  smoke  of  a  lamp,  in  order  that  the  operator 


94  ARTS   OF  ENGRAVING  AND  LITHOGRAPHY. 

may  see  the  progress  and  state  of  his  work.  The  instrument 
used  in  etching,  is  a  needle,  resembling  the  dry  point,  but  of 
different  sizes,  according  to  the  nature  of  the  work.  The  plate 
being  prepared,  the  operator  supporting  his  hand  on  a  ruler, 
begins  to  make  his  drawing  with  the  needle  in  the  coat  of  var- 
nish, taking  care  to  penetrate  always  to  the  copper.  In  the  use 
of  the  needle,  those  lines  which  require  to  be  deepest,  must 
have  the  greatest  force  bestowed  on  them,  but  it  is  not  possible 
to  produce  so  perfect  an  effect  in  this  way,  as  by  incisions  of 
the  graver.  After  the  design  is  completed,  the  operator  pro- 
ceeds to  the  second  part  of  the  process,  the  corrosion,  or  as  it 
technically  called  biting  in.  For  this  purpose,  the  plate  is  stir- 
rounded  with  a  w^all  of  soft  wax,  to  prevent  the  escape  of  fluid 
from  its  surface.  A  quantity  of  diluted  nitric  acid,  is  then 
poured  upon  it,  and  suffered  to  remain  for  some  time.  A  chemi- 
cal action  immediately  takes  place  in  all  the  lines  or  points  where 
the  copper  is  denuded  by  the  strokes  of  the  needle,  while  the 
rest  of  the  surface  is  defended  by  the  varnish.  In  the  mean 
time,  the  operator  brushes  the  surface  frequently,  with  a  feath- 
er, to  clear  away  the  bubbles  and  saturated  portions  of  the  met- 
al. After  the  first  biting  is  continued  for  a  sufficient  length  of 
time  in  the  judgment  of  the  operator,  the  acid  is  poured  off  and 
the  plate  examined.  The  light  shades,  if  found  sufficiently 
deep,  are  then  covered  with  varnish,  to  protect  them  from  fur- 
ther action  of  the  acid,  or  as  it  is  technically  called,  stopped 
out.  The  biting  is  then  continued  for  the  second  shades,  which 
are  next  stopped  out,  and  these  processes  are  alternately  repeat- 
ed till  the  piece  is  finished.  The  plate  is  then  freed  from  var- 
nish, by  melting  and  wiping  it,  and  cleansed  by  w^ashing  with 
oil  of  turpentine.  It  must,  in  this  state,  be  carefully  examined 
or  proved,  and  any  deficiencies  in  the  lines  owing  to  the  acci- 
dental presence  of  varnish,  must  be  finished  with  the  graver. 
The  plate  is  then  ready  for  the  press. 

The  productions  of  the  etching  needle,  can  never  have  the 
smoothness  and  beauty  of  mechanical  engravings.  Notwith- 
standing all  the  care  which  may  be  taken,  the  lines  will  have 


ARTS   OF   ENGRAVING  AND  LITHOGRAPHY. 


95 


an  irregularity  and  roughness,  owing  to  the  unequal  action  of 
the  acid.  There  are,  nevertheless,  subjects,  to  which  this  very 
irregularity  renders  etched  work  peculiarly  suited.  Those  ob- 
jects which  in  nature  are  rough,  and  coarse,  are  well  represent- 
ed by  this  species  of  engraving.  The  trunks  of  trees,  broken 
ground,  rocks,  walls,  cottages,  &;c.,  especially  when  executed 
on  a  large  scale,  receive  a  more  natural  aspect  from  the  rough 
effect  of  etching  than  they  could  do  without  great  labor  from 
the  softer  touches  of  the  graver.  In  landscape  engraving  we 
commonly  find  a  mixture  of  methods,  the  coarser  parts  being 
etched,  while  objects  of  more  delicacy  are  cut  with  the  graver. 
Letters  and  written  characters,  are  mostly  cut,  and  but  seldom 
etched. 

Mezzo  Tinto. — Engraving  in  mezzo  tinto,  or  mezzotint,  is 
the  fourth  species.  This  method  is  the  reverse  of  all  those 
hitherto  mentioned,  and  consists  in  bringing  up  lights  from  a 
dark  ground.  The  mezzo  tinto  was  invented  by  Prince  Ru- 
pert, in  1649.  Since  his  time,  it  has  been  greatly  improved, 
and  though  not  calculated  for  general  use,  it  has  been  applied 
to  various  subjects  with  great  success.  For  engraving  in  mez- 
zo tinto,  the  whole  surface  of  the  copperplate  is  first  roughen- 
ed or  covered  with  minute  prominences  and  excavations,  too 
small  to  be  obvious  to  the  naked  eye ;  so  that  if  an  impression 
be  taken  from  it  in  this  state,  it  has  an  uniform  velvety  black 
appearance.  This  roughness  is  produced  mechanically,  by  the 
operations  of  a  small  toothed  instrument  denominated  a  cradle. 
This  instrument  by  continual  turns  and  impressions,  which  oc- 
cupy a  great  length  of  time,  gradually  breaks  up  and  produces 
an  uniform  roughness  on  the  whole  surface  of  the  plate.  That 
the  ground,  as  it  is  called,  may  be  of  the  requisite  fineness,  the 
operation  must  be  repeated  a  considerable  number  of  times, 
the  position  of  the  plate  in  regard  to  the  instrument,  being  va- 
ried each  time.  This  is  the  most  tedious  part  of  the  labor. 
When  the  plate  is  prepared,  the  rest  of  the  process,  to  a  skilful 
engraver,  is  easy,  when  compared  with  cutting  or  stippling. 
It  consists  in  pressing  down  or  rubbing  out  the  roughness  of  the 


96 


ARTS  OF  ENGRAVING  AND  LITHOGRAPHY. 


plate,  by  means  of  the  burnisher  and  scraper,  to  the  extent  of 
the  intended  figure,  obliterating  the  ground  for  hghts,  and  leav- 
ing it  for  shades.  Where  a  strong  liglit  is  required,  the  whole 
ground  is  erased.  For  a  medium  light  it  is  moderately  burn- 
ished, or  partially  erased.  For  the  deepest  shades,  the  ground 
is  left  entire.  Care  is  taken  to  preserve  the  insensible  grada- 
tions of  light  and  shade  upon  which  the  effect  and  harmony  of 
the  piece  essentially  depend. 

Engraving  in  mezzo  tinto,  approaches  more  nearly  to  the  ef- 
fect of  oil  paintings  than  any  other  species.  It  is  well  calculat- 
ed for  the  representation  of  obscure  pieces,  such  as  night  scenes^ 
Sic.  Some  individuals  have  applied  it  with  good  success  to  the 
engraving  of  portraits.  The  principal  objection  to  the  method 
is,  that  the  plates  wear  out  speedily  under  the  press,  and  of 
course  yield  a  comparatively  small  number  of  impressions. 

Jlqua  Tinta. — Engraving  in  aqua  tinta,  is  the  only  remain- 
ing mode.  This  is  done  by  a  process  partly  chemical,  and 
partly  mechanical.  It  consists  in  producing  chemically,  a  rough 
ground  covering  the  surface  of  the  figure  to  be  engraved,  and 
afterwards  introducing  the  lights  and  shades  by  mechanical 
means.  It  may,  however,  be  executed  by  a  process  wholly 
chemical.  For  engraving  in  aquatint,  the  surface  of  the  copper, 
after  having  the  outline  engraved  or  etched  in  the  usual  way,  is 
covered  throughout  with  minute  particles  of  resin,  invisible  to 
the  naked  eye,  detached  from  each  other  and  adhering  to  the 
surface  of  the  metal.  This  process,  called  laying  the  ground, 
is  effected  in  different  ways.  One  method,  i&  to  inclose  a  quan- 
tity of  finely  powdered  rosin  or  mastic,  in  a  flannel,  or  linen 
bag.  This  is  held  at  a  certain  height  above  the  plate,  and  beat 
with  a  stick.  A  fine  cloud  of  dust  issues  from  the  bag,  and  set- 
tles upon  the  surface  of  the  plate,  with  the  same  uniformity  as 
the  dust  of  the  atmosphere  settles  upon  furniture  in  dry  weath- 
er. This  dust  is  fixed  to  the  surface,  by  heating  the  plate  till 
the  resin  melts.  The  ground  is  thus  laid.  A  second  mode,  is 
to  cov^r  the  plate  with  a  coat  of  very  thin  spirit  varnish  prepar- 
ed for  tlie  purpose.    This  varnish  is  so  fluid,  or  contains  so  little 


ARTS  OF  ENGRAVING  AND   LITHOGRAPHY.  97 

resin,  that  when  it  dries  by  the  evaporation  of  the  spirit,  the 
whole  surface  breaks  up,  or  cracks  into  an  infinite  number  of 
particles,  all  adhering  to  the  plate.  After  the  ground  is  com- 
pleted, the  vacant  parts  of  the  plate,  or  those  not  intended  to 
be  occupied  by  the  figure,  are  stopped  out ;  i.  e.  covered  by  a 
thick  varnish,  impenetrable  to  acid.  The  plate  is  now  sur- 
rounded by  a  wall  of  wax,  as  for  etching,  and  diluted  nitric  acid 
is  poured  on.  A  chemical  action  immediately  commences  in 
all  the  interstices  between  the  resinous  particles  ;  and  the  face  of 
the  plate,  for  the  desired  extent,  is  converted  into  a  porous  sur- 
face, made  up  of  little  prominences  and  excavations.  The 
lighter  shades  are  stopped  out  at  an  early  stage  of  the  process, 
and  the  corrosion  continued  for  the  dark  ones.  After  the  plate 
is  judged  to  be  sufficiently  bitten  in,  it  is  cleaned  and  proved  by 
an  impression.  If  the  ground  is  good,  i.  e.  not  too  faint,  too 
coarse,  or  too  uneven,  the  work  is  then  finished  by  burnishing 
the  shadings  to  give  them  greater  softness,  and  if  necessary,  by 
cutting  deep  lines  or  dots  in  the  darkest  parts. 

Engraving  in  aqua  tinta  has  the  greatest  resemblance  to  paint- 
ings in  water  colors,  or  in  India  ink.  When  well  executed,  the 
white  points  which  diversify  the  surface,  are  nearly  invisible  to 
the  naked  eye,  so  that  a  uniform  surface  is  presented.  The 
art  was  first  invented  by  a  Frenchman,  by  the  name  of  Leprince, 
who  for  some  time  kept  his  art  a  secret,  and  sold  his  impres- 
sions for  original  drawings.  It  is  a  mode  of  engraving  well 
adapted  to  light  subjects,  sketches,  landscapes,  &c.,  and  for 
subjects  of  which  only  a  few  copies  or  impressions  are  wanted. 
Owing  to  the  fineness  of  the  ground,  the  plates  wear  out  rapid- 
ly, and  seldom  yield,  when  of  the  ordinary  strength,  more  than 
600  impressions. 

Aqua  tinta  is  the  most  precarious  kind  of  engraving,  and  re- 
quires much  experience  and  attention  on  the  part  of  the  artist, 
to  succeed  well.  If  the  ground  is  laid  too  thick,  or  too  thin, 
the  result  is  imperfect.  If  the  corrosion  by  the  acid  is  not 
continued  long  enough,  the  ground  is  too  faint ;  if  continued 
00  long,  the  acid  acts  laterally,  and  destroys  the  whole  surface. 
^  13 


98 


ARTS   OF   ENGRAVING   AND  LITHOGRAPHY. 


It  is  often  necessary  to  repeat  the  whole  process,  and  to  go 
through  the  operations  of  laying  the  ground,  stopping  out,  and 
biting,  a  number  of  successive  times,  before  a  ground  is  obtain- 
ed of  sufficient  strength  and  regularity  to  answer  for  the  press. 

Copperplate  Printing. — Copperplate  printing  is  performed 
by  means  of  a  rolling  press,  in  which  the  plate  and  paper  are 
strongly  compressed  together  between  a  cylinder  of  wood  and 
a  sliding  platform.  The  ink  employed  for  copperplates,  is  made 
of  a  carbonaceous  substance  called  Frankfort  black,  and  linseed 
oil,  inspissated  by  boiling.  Oil  must  be  used,  instead  of  water, 
that  the  ink  may  not  dry  during  the  process  ;  it  is  boiled  till  it 
becomes  thick  and  viscid,  that  it  may  not  spread  upon  the  pa- 
per. Previously  to  the  operation,  the  paper  is  wet,  as  for 
printing  with  types.  The  printer  having  warmed  his  plate  over 
a  bed  of  coals,  proceeds  to  cover  its  surface  with  ink  by  an  in- 
strument resembling  a  printer's  roller.  When  the  cavities  of  the 
engraving  are  thoroughly  charged  with  ink,  the  smooth  surface 
of  the  plate  is  wiped  as  clean  from  ink  as  possible.  The  latter 
part  of  the  wiping  is  always  performed  by  the  palm  of  the  hand, 
aided  by  a  litde  dry  powder,  commonly  whiting.  The  ink  re- 
mains only  in  the  crevices  of  the  engraving,  into  which  the  hand 
does  not  penetrate  in  wiping  the  surface.  The  plate  is  next 
laid  on  the  sliding  plank,  with  its  face  upward,  and  the  paper 
laid  upon  it.  An  elastic  substance,  commonly  folds  of  woollen 
cloth,  is  placed  above  and  below.  A  turn  of  the  cylinder  car- 
ries the  plate  under  a  very  strong  pressure,  by  which  portions 
of  the  paper  are  forced  down  into  all  the  cavities  of  the  engrav- 
ing. The  ink,  or  a  part  of  it,  leaves  the  copper  and  adheres 
to  the  paper,  giving  an  exact  representation  of  the  whole  en- 
graving. 

Colored  Engravings. — Colored  engravings,  are  variously 
executed.  The  most  common,  are  printed  in  black  outline, 
and  afterward  painted  separately  in  water  colors.  Sometimes 
a  surface  is  produced  by  aqua  tinta,  or  stippling,  and  different 
colors  applied  in  printing  to  different  parts,  care  being  taken 
to  wipe  off  the  colors  in  opposite  directions,  that  they  may  not 


ARTS   OF  ENGRAVING   AND  LITHOGRAPHY. 


99 


interfere  with  each  other.  But  the  most  perfect,  as  well  as 
elaborate  productions,  are  those  which  are  first  printed  in  colors 
and  afterwards  painted  by  hand. 

Steel  Engraving, — The  process  of  steel  engraving,  intro- 
duced by  Mr  Perkins,  depends  on  the  property,  which  steel 
has,  of  being  softened,  by  losing  a  part  of  its  carbon  ;  and  af- 
terwards of  being  hardened,  by  regaining  it.  If  a  steel  plate, 
prepared  for  engraving,  be  inclosed  in  a  box  with  iron  filings, 
and  exposed  to  a  white  heat  for  some  hours,  the  surface  loses 
a  portion  of  carbon  and  becomes  sufficiently  softened  to  be  cut 
with  the  graver.  If  then  the  plate,  after  being  engraved,  is  re- 
exposed  to  heat  in  a  box  with  animal  charcoal,  the  surface  be- 
comes again  carbonated,  and  an  engraved  steel  plate  is  thus  ob- 
tained. 

The  great  advantage  of  steel  plates,  consists  in  their  hard- 
ness, by  which  they  last  for  an  indefinite  time,  and  yield  an  al- 
most unlimited  number  of  impressions ;  whereas  a  copperplate 
wears  out  after  two  or  three  thousand  impressions,  and  even  much 
sooner,  if  the  engraving  be  fine.  An  engraving  on  a  steel  plate, 
may  be  transferred  in  relief  to  a  softened  steel  cylinder,  by  pres- 
sure ;  and  this  cylinder,  after  being  hardened,  may  again  trans- 
fer the  design,  by  rolling  it  upon  a  fresh  steel  plate ;  and  thus 
the  design  may  be  multiplied  at  pleasure. 

Steel  engraving  is  of  use,  where  a  great  number  of  impres- 
sions are  called  for ;  as  it  saves  the  expense  of  engraving  the 
plate  anew,  and  furnishes  copies  more  exactly  resembling  each 
other,  than  can  be  obtained  by  any  other  mode.  Of  course  it 
affords  the  greatest  security  against  counterfeiting. 

Etching  on  steel  plates,  is  practised  with  various  chemical 
agents,  one  of  which  consists  of  a  mixture  of  six  parts  of  acetic 
acid,  with  one  of  nitric  acid.  Another  menstruum  is  made  by 
dissolving  an  ounce  of  corrosive  sublimate,  and  a  quarter  of  an 
ounce  of  alum,  in  half  a  pint  of  water. 

W ood  Engraving. — Engravings  in  wood,  are  differently  ex- 
ecuted from  those  already  described,  the  subjects  being  cut 
in  relief;  so  that  they  require  to  be  printed  in  the  same  manner 


100  ARTS  OF  ENGRAVING  AND  LITHOGRAPHY. 

as  common  types,  and  not  with  the  rolling  press.  The  material 
used  is  boxwood,  which  unites  the  properties  of  hardness,  fine- 
ness, and  density.  It  is  cut  across  the  grain  into  pieces  of  the 
height  of  common  types,  in  order  that  the  engraving  may  be 
made  upon  the  end  of  the  grain,  for  the  sake  of  strength  and 
durability.  The  surface  being  planed  very  smooth,  the  design 
is  drawn  upon  it  with  a  black  lead  pencil.  The  lines  of  this 
design  are  left  untouched,  but  the  whole  of  the  intermediate 
spaces  between  the  hues  are  cut  away  with  a  common  graver, 
or  chisel.  Wood  engravings  have  the  advantage  that  the  blocks 
may  be  inserted  in  a  page  with  common  types,  and  printed 
without  separate  expense.  They  are  exceedingly  durable,  and 
may,  if  desired,  be  multiplied  by  the  process  of  stereotyping. 

LITHOGRAPHY. 

Lithography  is  the  art  of  taking  impressions  from  drawings 
or  writings  made  on  stone,  without  engraving. 

Principles. — This  art  is  founded  on  the  property  which  stone 
possesses,  of  imbibing  fluids  by  capillary  attraction,  and  on  the 
chemical  repulsion  which  oil  and  water  have  for  each  other. 
A  drawing  is  first  made  on  stone  with  an  ink,  or  crayon,  of  an 
oily  composition,  and  the  surface  is  washed  over  with  water, 
which  sinks  into  all  the  parts  of  the  stone,  not  defended  by  the 
drawing.  A  cylindrical  roller,  charged  with  printing  ink,  is  then 
passed  over  the  surface  of  the  stone.  The  drawing  receives 
the  ink,  which  is  oily,  while  the  other  parts  of  the  stone  repel  it, 
being  defended  by  the  water.  The  process,  therefore,  depends 
entirely  on  chemical  principles,  and  is  thus  distinct  from  letter- 
press or  copperplate  printing,  which  are  mechanical.  On  this 
account,  it  has,  in  Germany,  been  called  chemical  printing. 

Origin. — The  invention  of  lithography  is  generally  ascribed 
to  Alois  Senefelder,  the  son  of  a  performer  at  the  Theatre  of 
Munich,  who  received  his  education  at  the  University  of  In- 
goldstadt.  Having  become  an  author,  and  being  too  poor  to 
publish  his  works,  he  tried  many  plans  with  copperplates,  and 


ARTS   OF  ENGRAVING  AND  LITHOGRAPHY.  101 

compositions,  and  accidentally  with  stone,  as  substitutes  for  let- 
ter-press, in  order  to  be  his  own  printer.  His  first  essays  to 
print  for  publication,  were  some  pieces  of  music,  executed  in 
1796,  after  which  he  attempted  various  drawings  and  writings.. 
The  first  productions  of  the  art  were  rude  and  of  little  promise. 
Its  progress,  however,  has  been  so  rapid,  that  it  now  gives  em- 
ployment to  a  vast  number  of  artists,  and  works  are  produced 
which  rival  the  finest  engravings,  and  even  surpass  them  in  the 
expression  of  certain  subjects. 

Lithographic  Stones. — As  calcareous  stones  will  all  imbibe 
oil  and  water,  and  receive  the  action  of  acids,  they  are  all 
capable  of  being  used  for  lithography.  Those,  however,  are 
best  adapted  to  the  purpose,  which  are  compact,  of  a  fine  and 
equal  grain,  and  free  from  veins,  or  imbedded  fossils  or  crys- 
tals.   A  conchoid al  fracture  is  considered  a  good  characteristic ► 

The  quarries  of  Solenhofen,  near  Pappenheim,  in  Bavaria^ 
furnished  the  first  plates,  and  none  have  as  yet  been  found  to 
equal  them  in  quality.  They  are  of  a  uniform,  pale  yellowish 
or  bluish  white  color,  and  the  fracture  is  perfectly  conchoid  al. 
Generally,  the  hardest  are  considered  best,  provided  they  are  uni- 
form in  texture.  Such  are  necessary  for  fine  chalk  drawings, 
while  softer  ones  answer  for  ink,  or  for  coarser  drawings  in 
chalk. 

In  France,  stones  have  been  found  near  Chateauroux,  of  a 
similar  color  to  those  of  Solenhofen,  and  even  harder,  and  of  a 
finer  grain,  but  they  are  full  of  spots  of  a  softer  nature,  so  that 
it  is  difficult  to  procure  pieces  of  the  necessary  size.  In  Eng- 
land, a  stone  has  been  used  for  lithography,  which  is  found  at 
Corston,  near  Bath.  It  is  one  of  the  white  lias  beds,  but  not 
so  fine  in  grain,  nor  so  close  in  texture  as  the  German  stone, 
and  therefore  inferior.  In  the  extensive  limestone  tracts  of  the 
United  States,  there  is  little  doubt  that  future  observation  will 
bring  to  light  stones  of  a  suitable  character  for  lithography. 

To  bear  the  pressure  used  in  taking  impressions,  a  stone 
twelve  inches  square,  should  be  an  inch  or  two  thick ;  and  the 
thickness  must  increase  with  the  size  of  the  stone. 


102  ARTS  OF  ENGRAVING  AND  LITHOGRAPHY. 


Preparation. — The  stones  are  first  ground  to  a  level  surface, 
by  rubbing  two  of  them  face  to  face  with  sand  and  water.  To 
prepare  them  for  ink  drawings,  they  are  next  polished  with 
pumice  stone.  But  when  they  are  intended  for  chalk  drawings, 
they  are  merely  ground  with  fine  sand,  which  has  been  passed 
through  a  sieve,  and  which  produces  a  smooth  and  uniform  sur- 
face, which  is  grained  and  not  polished,  this  surface  being  best 
adapted  for  holding  the  chalk. 

Lithographic  Ink  and  Chalk. — For  these  materials,  the  union 
of  several  qualities  is  required,  to  obtain  w^hich,  it  is  necessary 
to  combine  several  substances  together. 

For  hthographic  ink,  a  great  many  different  receipts  have 
been  given,  one  of  the  most  approved  of  which  is  a  com- 
position made  of  equal  parts  of  tallow,  wax,  shell  lac,  and  com- 
mon soap,  with  about  one  twentieth  part  of  the  whole,  of  lamp- 
black. These  materials  are  mixed  in  an  iron  vessel.  The 
wax  and  tallow,  are  first  put  in,  and  heated  till  they  take  fire, 
after  which,  the  other  ingredients  are  successively  added.  The 
burning  is  allowed  to  continue  until  the  composition  is  reduced 
about  one  third. 

Lithographic  chalk  should  have  the  qualities  of  a  good  draw- 
ing crayon ;  it  should  be  even  in  texture,  and  carry  a  good 
point.  The  following  proportions  are  among  the  best.  Soap, 
'  1^  oz. ;  tallow,  2  oz.;  wax,  1|  oz. ;  shell  lac,  1  oz. ;  lamp- 
black, \  oz.    The  manipulation  is  similar  to  that  for  the  ink. 

Mode  of  Drawing. — With  these  materials,  the  artist  proceeds 
to  work  on  the  prepared  stone,  after  wiping  it  with  a  dry  cloth. 
The  ink  being  rubbed  with  warm  water,  like  Indian  ink,  is  used 
on  the  polished  stone,  and  a  gradation  of  tints  can  be  obtained, 
only  by  varying  the  thickness  of  the  lines,  and  the  distance  at 
which  they  are  placed  apart.  It  is  necessary  to  mix  the  ink  to 
such  a  consistency,  that,  while  it  works  freely,  it  shall  yet  be 
strong  enough  to  stand  perfect,  through  the  process  of  printing. 
A  consistency,  a  little  greater  than  that  of  writing  ink,  is  suffi- 
cient for  this  purpose.  The  instruments  used  for  drawing  with 
ink,  are  steel  pens,  and  fine  camel's  hair  pencils. 


ARTS  OF   ENGRAVING   AND   LITHOGRAPHY.  103 

The  chalk  will  not  hold  upon  the  polished  stone.  But  the 
grained  stone  prepared  for  chalk,  may  be  drawn  upon  with  the 
chalk  crayon,  as  easily  as  paper.  The  subject  may  be  traced 
on  the  stone,  with  lead  pencil  or  red  chalk,  but  it  should  be 
done  so  lightly,  as  not  to  fill  up  any  of  the  grain  of  the  stone. 
In  drawing,  the  degree  of  pressure  of  the  hand  will  vary  the 
strength  of  the  tint,  and  it  is  desirable  to  give  the  requisite 
strength  at  once,  as  the  surface  of  the  stone  is  a  little  altered, 
by  receiving  the  chalk,  and  hence  it  does  not  take  any  addition- 
al lines  with  the  same  equality.  Practice  is  necessary  to  give 
a  command  of  the  material,  as  it  does  not  work  quite  like  the 
common  crayon,  there  being  great  difficulty  in  keeping  a  good 
point.  There  is  also  difficulty  in  obtaining  the  finer  tints  per- 
fect in  the  impression  ;  and  for  the  light  tints,  the  chalk  must 
be  used  in  a  reed,  as  the  metal  port-crayon  is  too  heavy  to  draw 
them,  even  without  any  pressure  from  the  hand.  A  scraper  is 
used  to  correct  errors,  and  also  to  produce  hghts. 

It  is  necessary  to  observe  that  the  grain  with  which  the  stone 
IS  prepared,  should  vary  with  the  fineness  of  the  drawing. 
Several  pieces  of  chalk  should  be  prepared  to  use  in  succession, 
as  the  warmth  of  the  hand  softens  it.  It  is  useful  to  cut  the 
chalk  to  the  form  of  a  wedge,  rather  than  a  point,  as  it  is  less 
likely  to  bend  in  that  form.  Small  portions  of  the  point  will 
break  off  during  the  drawing  ;  these  must  be  carefully  remov- 
ed with  a  small  brush. 

Etching  the  Stone. — After  the  drawing  is  finished  on  the  stone, 
as  before  described,  it  is  sent  to  the  lithographic  printer,  who 
proceeds  to  etch  the  drawing,  as  it  is  called.  The  stone  is  pla- 
ced obliquely  on  one  edge  over  a  trough,  and  very  dilute  nitric 
or  sulphuric  acid  is  poured  over  it.  The  degree  of  strength, 
which  is  little  more  than  one  per  cent,  of  acid,  should  be  such  as 
to  produce  a  very  slight  efFervesence.  The  object  of  this  shght 
etching  appears  to  be  to  produce  a  chemical,  rather  than  a  me- 
chanical change  of  surface,  and  it  is  by  some  considered  super- 
fluous, except  to  discharge  the  alkali  of  the  soap. 

The  stone  is  now  carefully  washed,  by  pouring  clean  rain 
water  over  it,  and  afterwards  gum  water  ;  and  when  not  too  wet, 


104 


ARTS   OF  ENGRAVING  AND  LITHOGRAPHY. 


the  roller,  charged  with  printing  ink,  is  rolled  over  it  in  both  di- 
rections, till  the  drawing  takes  the  ink.  It  is  then  well  covered 
with  a  solution  of  gum-arabic  in  water,  of  about  the  consisten- 
cy of  oil.  This  is  allowed  to  dry,  and  preserves  the  drawing 
from  any  alteration,  as  the  lines  cannot  spread,  in  consequence 
of  the  pores  of  the  stone  being  filled  with  gum. 

Printing. — When  the  stone  is  ready  for  the  press,  the  print- 
ing ink  is  applied  to  it,  by  means  of  an  elastic  roller,  covered 
with  leather.  In  the  lithographic  press,  the  paper  is  first  brought 
in  contact  with  the  stone,  and  protected  by  a  tight  cover  of 
strong  leather.  The  whole  is  then  passed  under  the  edge  of 
a  blunt  wooden  scraper,  which  is  powerfully  pressed  down  by  a 
double  lever,  and  thus  every  part  of  the  paper  is  successively 
brought  into  forcible  contact  with  the  stone,  and  an  accurate 
impression  received  of  the  drawing.  The  ink  is  then  reapplied 
to  the  stone,  and  the  process  repeated  for  each  impression. 

Printing  Ink, — This  is  composed,  as  other  printing  inks  are, 
of  oil-varnish,  and  fine  lamp  black.  To  prepare  the  varnish,  a 
vessel  is  about  half  filled  with  pure  hnseed  oil,  and  heated  till 
it  takes  fire  from  the  flame  of  a  piece  of  burning  paper.  It 
should  then  be  allowed  to  burn,  till  it  is  reduced  to  the  degree 
of  density  required. 

Remarks, — The  great  distinction  of  hthography  from  en- 
graving is,  that  it  gives  a  fac-simile  of  the  original  drawing, 
which  retains  the  freedom  and  touch  of  the  artist's  own  hand, 
while,  on  the  contrary,  an  engraving  must  be  a  copy.  This 
character  in  a  hthographic  print,  arises  from  the  facility  with 
which  the  drawing  is  produced,  as  the  process  is  exactly  that 
which  the  artist  would  follow,  in  making  a  common  drawing. 
A  further  advantage,  derived  from  the  same  cause,  is,  that  the 
drawing  being  made  at  once  on  the  stone,  the  whole  expense 
of  engraving  is  saved. 

The  more  finished  drawings  in  ink,  however,  have  not  the 
same  advantages,  for  the  gradations  can  only  be  obtained  by  the 
variations  in  the  breadth  and  the  distance  of  the  lines,  which  is 


ARTS   OF  ENGRAVING  AND   LITHOGRAPHY.  105 

the  same  principle  as  that  on  which  the  engraver  works ;  and 
hence  the  labor  is  more  nearly  equal  in  the  two  methods. 

The  number  of  impressions,  which  can  be  taken  from  a  li- 
thographic chalk  drawing,  will  vary  according  to  the  fineness  of 
the  tints.  A  fine  drawing,  will  give  400,  or  500 ;  a  strong 
one,  1000,  or  1500.  Ink  drawings,  and  writings,  give  consid- 
erably more  than  copperplates.  The  finest  will  yield  6000,  or 
8000,  and  strong  lines,  and  writings,  many  more.  Upwards  of 
80,000  impressions  have  been  taken  at  Munich,  from  one  writ- 
ing, of  a  form  for  regimental  returns. 

A  method  has  been  introduced,  by  which  copies  of  valuable 
engravings  may  be  multiplied  indefinitely.  An  impression  on 
paper,  is  taken,  in  the  usual  manner,  from  the  copperplate,  and 
immediately  laid  with  its  surface  upon  water.  When  sufficient- 
ly wet,  it  is  carefully  applied  to  the  surface  of  a  stone,  pre- 
pared in  the  usual  manner,  and  pressed  down  upon  it  by  the 
application  of  a  roller,  till  the  ink  leaves  the  paper,  and  adheres 
to  the  stone.  It  is  then  printed  in  the  common  way.  Auto- 
graphic writings  may  be  transferred  from  paper  to  stone,  and 
printed  in  a  manner  nearly  similar. 


Land  seer's  Lectures  on  Engraving,  8vo.  London,  1807 ; — Meadows, 
Lectures  on  Engraving,  London,  1811; — Partington's  Mechanic's 
Gallery,  8vo.  1825; — Rees's  Cyclopaedia,  under  the  various  heads  ; — 
Hulmandel's  Treatise  on  Lithography,  8vo.  1817; — Senefelder's 
Complete  Course  of  Lithography,  4to.  ; — London  Journal  of  Arts,  pas- 
sim',— De  Lastetrie,  Journal  de  Connaisances  usuellesj  translated 
Franklin  Journal,  vol.  iv. 


14 


CHAPTER  VI. 

OF  SCULPTURE,  MODELLING,  AND  CASTING. 

Subjects. — Sculpture  in  its  most  general  sense,  is  the  art  of 
producing  resemblances  of  visible  forms,  out  of  solid  materials. 
The  required  shapes  are  produced  by  carving,  when  the  mate- 
rial is  solid  and  brittle ;  and  to  this  sense  the  term  sculpture  is 
sometimes  hmited.  They  are  also  formed  by  modelling,  when 
the  material  is  soft ;  and  by  casting,  when  it  is  liquid,  or  fusi- 
ble. The  productions  of  this  art  are  known  under  various  de- 
nominations, according  to  their  character  and  subject.  Of 
these,  the  most  important  are  statues,  which  are  entire  resem- 
blances of  living  objects.  Busts  consist  of  the  upper  portions 
of  statues.  Bas-reliefs,  in  the  common  acceptation  of  the  term, 
are  partial  sculptures,  or  lateral  views  of  figures,  raised  upon  a 
plane  surface.  Their  different  degrees  of  prominence  are  dis- 
tinguished by  the  Italians,  under  different  names.  These  are, 
alto  relievo,  or  high  rehef,  when  the  figures  are  nearly  complete, 
or  appear  to  issue  from  the  back  ground  ;  mezzo  relievo,  or 
middle  relief,  in  which  they  are  half  raised  from  the  surface ; 
and  basso  relievo,  low  relief,  or  bas-relief  properly  so  called, 
when  the  figures  have  not  the  prominence  which  their  outline 
requires,  but  appear  as  if  compressed.  The  principal  remain- 
ing objects  of  sculpture,  are  vases,  armatures,  or  trophies,  and 
the  decorative  parts  of  architecture. 

Modelling. — Before  any  object  is  executed  in  stone,  it  is  the 
practice  of  sculptors,  to  complete  a  representation  of  their  de- 
sign, by  modelling  it  in  clay,  or  some  other  soft  material.  The 
genius  of  the  artist  is  displayed  altogether  in  the  model,  for  the 
process  of  afterwards  copying  the  model  in  stone,  is  chiefly 
mechanical,  and  may  often  be  executed  by  another  person,  as 


OF   SCULPTURE,  MODELLING,   AND   CASTING.  107 


well  as  by  the  sculptor  himself.  When  a  clay  model  is  under- 
taken, if  the  proposed  figure  be  large,  a  frame  of  wood  or  iron 
is  erected  to  give  support  to  the  limbs  and  different  parts  of  the 
figure.  Upon  this  frame,  a  proper  quantity  of  wet  clay  is  dis- 
tributed, and  wrought  into  the  form  of  the  intended  statue. 
The  moulding  of  the  clay  is  performed  with  the  hands,  and 
with  various  instruments  of  wood  and  ivory.  When  the  mod- 
el is  completed,  copies  may  be  taken  from  it,  either  by  casting 
them  in  plaster,  or  in  metal ;  or  by  chiseling  them  in  marble. 

Casting  in  Plaster. — Copies  are  most  frequently  taken,  both 
from  new  models,  and  from  old  statues,  by  casting  them  in 
plaster.  For  this  purpose  a  mould  in  plaster  is  first  made  from 
the  surface  of  the  statue,  or  figure,  itself;  and  this  mould  is  af- 
terwards used  to  reproduce  the  figure  by  casting.  Plaster  is 
prepared  for  use  by  pulverizing  common  gypsum,  and  expos- 
ing it  to  the  heat  of  a  fire  until  its  moisture  is  wholly  expelled.* 
While  in  this  dry  state,  if  it  be  mixed  with  water  to  the  consis- 
tence of  cream  or  paste,  it  has  the  property  of  hardening  in  a 
few  minutes,  and  takes  a  very  sharp  impression.  The  hard- 
ness afterwards  increases  by  keeping,  till  it  approaches  the 
character  of  stone. 

Moulds  are  formed  in  the  following  manner.  The  statue  or 
figure  to  be  copied,  is  first  oiled,  to  prevent  it  from  cohering 
with  the  gypsum.  A  quantity  of  Hquid  plaster  sufiEicient  for  the 
mould,  is  then  poured  on,  immediately  after  being  mixed,  and 
is  suffered  to  hardefi.  If  the  subject  be  a  bas-relief,  or  any 
figure  which  can  be  withdrawn  without  injury,  the  mould  may 
be  considered  as  finished,  requiring  only  to  be  surrounded  with 
an  edging.  But  if  it  be  a  statue,  it  cannot  be  withdraw^n,  with- 
out breaking  the  mould,  and  on  this  account  it  becomes  neces- 
sary to  divide  the  mould  into  such  a  number  of  pieces,  as  will 
separate  perfectly  from  the  original.    These  are  taken  off  from 

*  The  heat  requisite  for  this  purpose  must  be  greater  than  that  of  boiling 
water.  Care  must  be  taken  not  to  raise  the  heat  too  high,  as  in  that  case  the 
sulphate  of  lime  would  be  decomposed. 


108  OF   SCULPTURE,   MODELLING,  AND  CASTING. 

the  statue,  and  when  afterwards  replaced,  or  put  together,  with- 
out the  statue,  they  constitute  a  perfect  mould.  This  mould, 
its  parts  having  been  oiled  to  prevent  adhesion,  is  made  to  re- 
ceive a  quantity  of  plaster,  by  pouring  it  in  at  a  small  orifice. 
The  mould  is  then  turned  in  every  direction,  in  order  that  the 
plaster  may  fill  every  part  of  the  surface ;  and  when  a  sufficient 
quantity  is  poured  in  to  produce  the  strength  required  in  the 
Cftst,  the  remainder  is  often  left  hollow,  for  the  sake  of  lightness, 
and  economy  of  the  material.  When  the  cast  is  dry,  it  is  ex- 
tricated by  separating  the  pieces  of  the  mould,  and  finished  by 
removing  the  seams  and  blemishes  with  the  proper  tools.  *  If 
the  form  or  position  require  it,  the  limbs  are  cast  separately, 
and  afterwards  cemented  on. 

Moulds  and  busts  are  obtained  in  a  similar  manner  from  liv- 
ing faces,  by  covering  them  with  new  plaster,  and  removing  it 
in  pieces  as  soon  as  it  becomes  hard.  It  is  necessary  that  the 
skin  of  the  face  should  be  oiled,  and  during  the  operation,  the 
eyes  are  closed,  and  the  person  breathes  through  tubes  inserted 
in  the  nostrils. 

Elastic  moulds  have  been  formed  by  pouring  upon  the  figure 
to  be  copied,  a  strong  solution  of  glue.  This  hardens  upon 
cooling,  and  takes  a  fine  impression.  It  is  then  cut  into  suita- 
ble pieces  and  removed.  The  advantage  of  the  elastic  mould 
is  that  it  separates  more  easily  from  irregular  surfaces,  or  those 
with  uneven  projections  and  under  cuttings,  from  which  a  com- 
mon mould  could  not  be  removed  without  violence,  f 

*  Plaster  casts  are  varnished  by  a  mixture  of  soap  and  white  wax  in  boiling 
water.  A  quarter  of  an  ounce  of  soap  is  dissolved  in  a  pint  of  water,  and  an 
equal  quantity  of  wax  afterwards  incorporated.  The  cast  is  dipped  in  this 
liquid,  and  after  drying  a  week,  is  polished  by  rubbing  with  soft  linen.  The 
surface  produced  in  this  manner  approaches  to  the  polish  of  marble. 

When  plaster  casts  are  to  be  exposed  to  the  weather,  their  durability  is  great- 
ly increased  by  saturating  them  with  linseed  oil,  with  which  wax  or  rosin  may 
be  combined.  When  intended  to  resemble  bronze,  a  soap  is  used,  made  of 
linseed  oil  and  soda  colored  by  the  sulphates  of  copper  and  iron.  Walls  and 
ceilings  are  rendered  water  proof  in  the  same  way.  See  an  abstract  of  a 
memoir  of  D'  Arcet  and  Thenard,  in  Brande's  Journal,  vol.  xxii.  184,  and 
Franklin  Journal,  ii.  276. 

t  See  a  paper  by  Mr  Fox,  republished  in  the  Franklin  Journal,  vol.  iii. 


OF   SCULPTURE,   MODELLING,   AND   CASTING.  109 


For  small  and  delicate  impressions,  which  are  merely  in  re- 
lief, melted  sulphur  is  sometimes  used,  also  a  strong  solution  of 
isinglass  in  proof  spirit.  The  latter  material  has  the  advantage 
that  it  is  not  brittle  when  dry,  but  possesses  a  consistence  like 
that  of  horn.  Both  substances  yield  very  accurate  and  sharp 
impressions. 

Bronze  Casting. — Statues  intended  to  occupy  situations  in 
which  they  may  be  exposed  to  violence,  are  commonly  made 
of  bronze.  This  material  resists  both  mechanical  injuries,  and 
decay  from  the  influence  of  the  atmosphere.  The  moulds  in 
which  bronze  statues  are  cast,  are  made  on  the  pattern,  out  of 
plaster  and  brick  dust,  the  latter  material  being  added  to  resist 
the  heat  of  the  mehed  metal.  The  parts  of  this  mould  are 
covered  on  their  inside  with  a  coating  of  clay,  as  thick  as  the 
bronze  is  intended  to  be.  The  mould  is  then  closed,  and  filled 
on  its  inside  with  a  nucleus  or  core  of  plaster  and  brick  dust, 
mixed  with  w^ater.  When  this  is  done,  the  mould  is  opened, 
and  the  clay  carefully  removed.  The  mould  with  its  core,  are 
then  thoroughly  dried,  and  the  core  secured  in  its  central  posi- 
tion by  short  bars  of  bronze  which  pass  into  it  through  the  ex- 
ternal part  of  the  mould.  The  whole  is  then  bound  with  iron 
hoops,  and  when  placed  in  a  proper  situation  for  casting,  the 
melted  bronze  is  poured  in  through  an  aperture  left  for  the  pur- 
pose. Of  course  the  bronze  fills  the  same  cavity  which  was 
previously  occupied  by  the  clay,  and  forms  a  metalhc  covering 
to  the  core.  This  is  afterwards  made  smooth  by  mechanical 
means. 

Practice  of  Sculpture. — To  execute  a  statue  in  marble,  which 
shall  exactly  correspond  to  a  pattern  or  model,  is  a  work  of  me- 
chanical, rather  than  of  inventive  skill.  It  is  performed  by  find- 
ing, in  the  block  of  marble,  the  exact  situation  of  numerous 
points  corresponding  to  the  chief  elevations  and  cavities  in  the 
figure  to  be  imitated,  and  joining  these  by  the  proper  curves 
and  surfaces  at  the  judgment  of  the  eye.  These  points  are 
found,  by  measuring  the  height,  depth,  and  lateral  deviation  of 
the  corresponding  points  in  the  model ;  after  which,  those  in 


110  OF  SCULPTURE,  MODELLING,  AND  CASTING. 


the  block  are  found  by  similar  measurements.  Sometimes  the 
points  are  ascertained,  by  placing  the  model  horizontally  under 
a  frame,  and  suspending  a  plumb  line  successively  from  differ- 
ent parts  of  the  frame,  till  it  reaches  the  parts  of  the  figure  be- 
neath it.  Sometimes  an  instrument  is  used  consisting  of  a 
moveable  point,  attached  by  various  joints  to  an  upright  post,  so 
that  it  may  be  carried  to  any  part  of  the  statue,  and  indicate 
the  relative  position  of  that  part  in  regard  to  the  post.  Ma- 
chines have  also  been  contrived  for  cutting  any  required  figure 
from  a  block,  the  cutting  instrument  being  directed  by  a  guage 
which  rests  upon  the  model  in  another  part  of  the  machine. 

Marble  is  wrought  to  the  rough  outline  of  the  statue,  by  the 
chisel  and  hammer,  aided  by  the  occasional  use  of  drills  and 
other  perforating  tools.  It  is  then  smoothed  with  rasps  and  files, 
and  when  required,  is  polished  with  pumice  stone  and  putty. 
The  hair  of  statues  is  always  finished  with  the  chisel,  and  for 
•this  object,  very  sharp  instruments  with  different  points  and 
edges  are  necessary.  The  ancient  sculptors  appear  to  have  re- 
lied almost  wholly  upon  the  chisel,  and  to  have  used  that  instru- 
ment with  great  boldness  and  freedom,  such  as  could  have  been 
justified  only  by  consummate  skill  in  the  art.  The  moderns,  on 
the  contrary,  approach  the  surface  of  the  statue  with  great  cau- 
tion, and  employ  safer  means  for  giving  the  last  finish.  Some 
of  the  most  celebrated  antique  statues,  such  as  the  Laocoon, 
the  Apollo  Belvidere,  and  Venus  de  Medicis,  are  thought  to 
have  been  finished  with  the  chisel  alone. 

Materials. — Although  marble  has  been  the  common  material 
of  sculpture,  both  in  ancient  and  modern  times,  yet  other  sub- 
stances have  been  occasionally  made  subjects  of  the  chisel. 
Statues  of  porphyiy,  granite,  serpentine,  and  alabaster,  are 
found  among  the  remains  of  antiquity.  Other  materials  of  a 
less  durable  kind,  were  also  employed.  Some  of  the  principal 
works  of  Phidias  were  made  of  ivory  and  gold,  particularly 
his  colossal  statues  of  Jupher  Olympius,  and  Minerva,  at 
Athens. 


OF  SCULPTURE,  MODELLING,   AND   CASTING.  Ill 


Ohjecis  of  Sculpture. — In  sculpture,  as  in  the  other  imitative 
arts,  two  ends  propose  themselves  to  the  skill  of  the  artist. 
One  consists  in  the  imitation  of  a  particular  object,  in  which 
case  the  art  of  the  sculptor  can  be  expected  only  to  equal,  but 
not  to  surpass,  his  original.  The  other  consists  in  new  combi- 
nations of  excellence,  and  in  the  invention  of  forms  and  ex- 
pressions, which  are  not  known  to  exist  together  in  nature,  but 
are  embodied  in  the  imagination  of  the  artist.  Beauty  in  ob- 
jects thus  conceived,  constitutes  the  beau  ideal  in  art,  to  attain 
which,  has  ever  been  the  ambition  of  cuhivators  of  the  fine 
arts.  In  statuary,  the  specimens  which  have  descended  to  us 
from  the  ancient  Greeks,  are  by  universal  consent  admitted  to 
be  the  most  perfect  designs  of  beauty,  and  furnish  the  common 
models  for  study  and  imitation,  at  the  present,  as  in  all  former 
ages. 

Gem  Engraving. — The  art  of  cutting  precious  stones,  is 
more  properly  a  species  of  sculpture,  than  of  engraving.  The 
hardness  of  these  stones  renders  it  impossible  to  operate  on 
them  by  the  strongest  steel  instrimnents.  They  are  therefore 
wrought  in  a  slow  manner,  by  grinding  them  away  upon  the 
surface  of  a  wheel,  commonly  made  of  metal,  and  covered  with 
the  grit,  or  fine  powder  of  some  hard  substance.  The  diamond 
can  only  be  ground,  or  cut,  with  its  own  dust.  Rubies,  agates, 
emeralds,  Sic,  are  cut  and  polished  with  emery  or  tripoli,  in 
fine  powder.  Lapidaries  make  use  of  small  wheels,  balls,  and 
drills,  of  various  forms,  made  of  iron,  or  copper,  which  revolve 
with  great  rapidity,  and  act  upon  the  stone  through  the  medium 
of  the  pulverized  material  on  their  surface.  They  also  use 
wires  covered  with  emery,  for  the  purpose  of  sawing  plates. 

The  imitative  designs,  which  are  cut  upon  hard  stones,  are 
chiefly  of  two  kinds.  The  first  of  these  are  cameos,  which  are 
little  bas-reliefs  or  figures,  raised  above  the  surface.  They  are 
commonly  made  from  stones,  the  strata  of  which  are  of  differ- 
ent colors,  so  that  the  raised  figure  is  of  a  different  color  from 
the  ground  to  which  it  is  attached.  Varieties  of  agate,  carne- 
lian,  onyx,  he,  are  made  use  of  for  this  purpose.  Sometimes 


112  OF  SCULPTURE,  MODELLING,  AND  CASTING. 


several  successive  strata  of  different  colors,  are  so  wrought  as 
to  produce  the  appearance  of  painting.  A  cheaper  kind  of  ca- 
meos are  made  from  marine  shells.  These  having  lime  for 
their  basis,  may  be  scratched  with  steel,  or  corroded  with  acids. 
Intaglios  are  the  second  kind  of  engraved  gems.  They  differ 
from  cameos  in  having  the  figure  cut  into,  or  below,  the  surface,  > 
so  that  they  serve  as  seals  to  produce  impressions  in  relief  upon 
soft  substances. 

Mosaic. — Mosaics  are  imitations  of  paintings  made  by  com- 
bining together  an  infinite  number  of  minute  stones  of  different 
colors,  and  cementing  them  on  a  plane  surface.  In  the  most  cost- 
ly mosaics,  precious  stones  have  been  cut,  and  arranged  to  pro- 
duce this  effect.  But  in  common  works  of  this  art,  enamels  of 
different  colors,  manufactured  for  the  purpose,  are  the  material 
employed.  The  enamel  is  first  formed  into  sticks,  from  the 
ends  of  which  pieces  of  the  requisite  size  are  cut,  or  broken  off. 
These  are  confined  in  their  proper  places  upon  a  plate  of  met- 
al or  stone,  by  a  cement  made  of  quicklime,  pulverized  lime- 
stone, and  linseed  oil.  After  the  whole  has  adhered,  it  is  al- 
lowed to  dry  two  months,  and  is  then  polished  with  a  flat  stone 
and  emery.  *  Inlaid  works  of  agate,  and  other  costly  stones, 
are  executed  on  the  same  principle  as  mosaic  ;  except  that  the 
stones  are  larger  and  cut  to  the  shape  of  different  parts  of  the 
object  to  be  represented,  whereas  in  mosaic,  the  pieces  are  of 
the  same  size  and  shape.  The  opus  reticulatum  of  the  ancients, 
with  which  columns  and  walls  were  sometimes  incrusted,  is 
found  to  consist  of  small  stones  of  a  pyramidal  form,  the  apex 
of  which  is  imbedded  in  mortar,  while  the  base,  which  is  pol- 
ished, forms  the  outer  surface. 

Scagliola. — This  name  is  given  at  Rome,  to  a  sort  of  artifi- 
cial inlaid  work,  composed  of  plaster,  but  resembling  stone. 
For  works  of  this  kind,  gypsum,  dried  and  powdered,  is  mixed 

*  One  of  the  largest  mosaics  which  has  been  executed,  is  a  copy  of  Leonar- 
do da  Vinci's  celebrated  picture  of  the  last  supper.  It  measures  24  feet  by  12, 
and  employed  eight  or  ten  artists  for  eight  years.  It  was  executed  under  the 
direction  of  Raffaelli,  at  Milan,  by  order  of  the  French  government.  Cadell. 


OF   SCULPTURE,  MODELLING,   AND   CASTING.  113 


with  a  solution  of  glue,  and  s})read  on  a  tablet  for  the  ground 
of  the  picture.  Cavities  of  the  form  intended  in  the  design, 
are  then  made  in  it  with  an  engraving  tool.  These  are  succes- 
sively filled  up  with  portions  of  plaster  of  different  colors,  so 
managed  as  to  produce  the- effect  of  painting.  In  this  way- 
buildings,  and  various  natural  objects  are  represented.  The 
surface  is  finely  polished,  by  rubbing  it  with  different  powders, 
and  where  the  ground  is  white,  with  rushes. 


WiNCKELMANN,  Histolrt  dt  V  M  chez  les  Anciens,  3  vols,  4to.  tr. 
1802; — MiLLiN,  Dictionnaire  des  Beaux  Arts,  3  vols,  8vo.  1806; — 
Rees's  Cyclopaedia ; — Works  of  Vasari  ; — Quatremere  de  Quin- 
CY — Cicognara — ViscoNTi,  &c. ; — Travels,  and  works  of  Clarke — 
Eustace — Cadell — Dodwell — Stuart — Elgin,  ^c.  &c. 


15 


CHAPTER  VII. 

OF  ARCHITECTURE  AND  BUILDING. 

Architecture, — Architecture,  in  its  most  general ^ense,  is  the 
art  of  erecting  buildings,  of  any  kind.  In  modern  use,  this 
name  is  sometimes  restricted  to  the  external  forms,  or  styles,  of 
building,  in  which  sense,  architecture  is  one  of  the  fine  arts. 
It  appears  to  have  been  among  the  earliest  inventions,  and  its 
works  have  been  commonly  regulated  by  some  principle  of 
hereditary  imitation.  Whatever  rude  structure  the  climate  and 
materials  of  any  country  have  obliged  its  early  inhabitants  to 
adopt  for  their  temporary  shelter,  the  same  structure,  with  all 
its  prominent  features,  has  been  afterwards  kept  up  by  their  refin- 
ed, and  opulent  posterity.  Thus,  the  Egyptian  style  of  building 
has  its  origin  in  the  cavern  and  mound ;  the  Chinese  architec- 
ture is  modelled  from  the  tent ;  the  Grecian,  is  derived  from  the 
wooden  cabin,  and  the  Gothic,  from  the  hower  of  trees. 

Elements. — The  essential  elementary  parts  of  a  building,  are 
those  which  contribute  to  its  support,  inclosure,  and  covermg. 
Of  these,  the  most  important  are  the  foundation,  the  column, 
the  wall,  the  lintel,  the  arch,  the  vault,  the  dome,  and  the  roof. 

Foundations. — In  laying  the  foundation  of  any  building,  it  is 
necessary  to  dig  to  a  certain  depth  in  the  earth,  to  secure  a  sol- 
id basis,  below  the  reach  of  frost  and  common  accidents.  The 
most  'solid  basis  is  rock,  or  gravel  which  has  not  been  moved. 
Next  to  these,  are  clay  and  sand,  provided  no  other  excavations 
have  been  made  in  the  immediate  neighborhood.  From  this 
basis,  a  stone  wall  is  carried  up  to  the  surface  of  the  ground, 
and  constitutes  the  foundation.    Where  it  is  intended  that  the 


*  Wilkins'  Vitruvius.  p.  xvii. 


OF  ARCHITECTURK   AND  KUILDINC;.  11^ 

superstructure  shall  press  unequally,  as  at  its  piers,  chirniiies,  or 
columns,  it  is  sometimes  of  use  to  occupy  the  space  between 
the  points  of  pressure,  by  an  inverted  arch.  This  distributes 
the  pressure  equally,  and  prevents  the  foundation  from  spring- 
ing between  the  different  points.  In  loose  or  muddy  situations, 
it  is  always  unsafe  to  build,  unless  we  can  reach  the  solid  bot- 
tom below.  In  salt  marshes  and  flats,  this  is  done  by  deposit- 
ing timbers,  or  driving  wooden  piles,  into  the  earth,  and  raising 
walls  upon  them.  The  preservative  quality  of  the  salt,  will 
keep  these  timbers  unimpaired  for  a  great  length  of  time,  and 
makes  the  foundation  equally  secure  with  one  of  brick  or 
stone. 

Column. — The  simplest  member  in  any  building,  though  by 
no  means  an  essential  one  to  all,  is  the  column,  or  pillar. 
This  is  a  perpendicular  part,  commonly  of  equal  breadth  and 
thickness,  not  intended  for  the  purpose  of  inclosure,  but  simply 
for  the  support  of  some  part  of  the  superstructure.  The  prin- 
cipal force  which  a  column  has  to  resist,  is  that  of  perpendicular 
pressure.  In  its  shape,  the  shaft  of  a  column  should  not  be 
exactly  cylindrical,  but  since  the  lower  part  must  support  the 
weight  of  the  superior  part,  in  addition  to  the  weight  which 
presses  equally  on  the  whole  column,  the  thickness  should  grad- 
ually decrease  from  bottom  to  top.  The  outline  of  columns, 
should  be  a  litde  curved,  so  as  to  represent  a  portion  of  a  very 
long  spheroid,  or  paraboloid,  rather  than  of  a  cone.  This  fig- 
ure is  the  joint  result  of  two  calculations,  independent  of  beauty 
of  appearance.  One  of  these  is,  that  the  form  best  adapted 
for  stability  of  base,  is  that  of  a  cone.  The  other  is,  that  the 
figure  which  would  be  of  equal  strength  throughout  for  sup- 
porting a  superincumbent  weight,  would  be  generated  by  the 
revolution  of  two  parabolas  round  the  axis  of  the  column,  the 
vertices  of  the  curves  being  at  its  extremities.  * 


*Sec  Tredgold's  Principles  of  Carpentry,  p.  50, 


116 


OF  ARCHITECTURE  AND  BUILDING. 


f  

— f 

1  1 

1 

1 

1  1 

1  2  3 


In  the  accompanying  wood  cut,  No.  1  is  the  figure  having 
the  greatest  stability  of  base ;  2,  the  figure  which  is  of  equal 
strength  throughout  for  resisting  vertical  pressure,  and  3,  the  in- 
termediate, or  common  form  of  the  column,  a  little  more  curv- 
ed than  is  usual  in  practice,  and  having  its  top  truncated  to  give 
stability  to  the  entablature. 

The  swell  of  the  shafts  of  columns,  was  called  the  entasis^ 
by  the  ancients.  It  has  been  lately  found,  *  that  the  columns 
of  the  Parthenon,  at  Athens,  which  have  been  commonly  sup- 
posed straight,  deviate  about  an  inch  from  a  straight  line,  and 
that  their  greatest  swell  is  at  about  one  third  of  their  height. 

Columns  in  the  antique  orders,  are  usually  made  to  diminish 
one  sixth,  or  one  seventh,  of  their  diameter,  and  sometimes  even 
one  fourth.  The  Gothic  pillar  is  commonly  of  equal  thick- 
ness throughout. 

Wall. — The  wall,  another  elementary  part  of  a  building, 
may  be  considered  as  the  lateral  continuation  of  a  colum.n,  an- 
swering the  purpose  both  of  inclosure  and  support.  A  wall 
must  diminish  as  it  rises,  for  the  same  reasons,  and  in  the  same 
proportion,  as  the  column.  It  must  diminish  still  more  rapidly 
if  it  extends  through  several  stories,  supporting  weights  at  dif- 
ferent heights.  A  wall,  to  possess  the  greatest  strength,  must 
also  consist  of  pieces,  the  upper  and  lower  surfaces  of  which 
are  horizontal  and  regular,  not  rounded  nor  oblique.  The 
walls  of  most  of  the  ancient  structures,  which  have  stood  to 
the  present  time,  are  constructed  in  this  manner,  and  frequent- 
ly have  their  stones  bound  together  with  bolts  and  cramps 

*  By  Messrs  AUason  and  Cockerel.    See  Brande's  Journal,  vol.  x.  p  204. 


OF  ARCHITECTURE   AND  RTJILDING. 


117 


of  iron.  The  same  method  is  adopted  in  such  modern  struc- 
tures as  are  intended  to  possess  great  strength  and  durability, 
and  in  some  cases  the  stones  are  even  dovetailed  together,  as  in 
the  light  houses  at  Eddystone,  and  Bell  JRock.  But  many  of 
our  modern  stone  walls,  for  the  sake  of  cheapness,  have  only 
one  face  of  the  stones  squared,  the  inner  half  of  the  wall  being 
completed  with  brick ;  so  that  they  can  in  reality  be  considered 
only  as  brick  walls  faced  with  stone.  Such  walls  are  said  to  be 
liable  to  become  convex  outwardly,  from  the  difference  in  the 
shrinking  of  the  cement. 

Rubble  walls,  are  made  of  rough,  irregular  stones  laid  in- 
mortar.  The  stones  should  be  broken,  if  possible,  so  as  to 
,  produce  horizontal  surfaces.  The  coffer  walls  of  the  ancient  Ro- 
mans were  made  by  inclosing  successive  portions  of  the  intend- 
ed wall  in  a  box,  and  filh"ng  it  with  stones,  sand,  and  mortar, 
promiscuously.  This  kind  of  structure  must  have  been  ex- 
tremely insecure.  The  Pantheon,  and  various  other  Roman 
buildings,  are  surrounded  with  a  double  brick  wall,  having  its 
vacancy  filled  up  with  loose  bricks  and  cement.  The  whole 
has  gradually  consolidated  into  a  mass  of  great  firmness.  The 
reticulated  w^alls  of  the  Romans,  having  bricks  wdth  oblique  sur- 
faces, would  at  the  present  day  be  thought  highly  unphilosophi- 
cal.  Indeed  they  could  not  long  have  stood,  had  it  not  been 
for  the  great  strength  of  their  cement. 

Modern  brick  walls  are  laid  with  great  precision,  and  de- 
pend for  firmness  more  upon  their  position  than  upon  the 
strength  of  their  cement.  The  bricks  being  laid  in  horizontal 
courses,  and  continually  overlaying  each  other,  or  breaking 
joints^  the  whole  mass  is  strongly  interwoven,  and  bound  to- 
gether. Wooden  walls,  composed  of  timbers  covered  with 
boards,  are  a  common,  but  more  perishable  kind.  They  re- 
quire to  be  constantly  covered  with  a  coating  of  a  foreign  sub- 
stance, as  paint  or  plaster,  to  preserve  them  from  spontaneous 
decomposition. 

In  some  parts  of  France,  and  elsewhere,  a  kind  of  wall  is 
made  of  earth,  rendered  compact  by  ramming  it  in  moulds  or 


118  OF  ARCHITECTURE  AND  BUILDING. 


cases.  This  method  is  called  building  in  Pise,  and  is  much 
more  durable  than  the  nature  of  the  material  would  lead  us  to 
suppose. 

Walls  of  all  kinds  are  greatly  strengthened  by  angles  and 
curves,  also  by  projections,  such  as  pillasters,  chimnies,  and 
buttresses.  These  projections  serve  to  increase  the  breadth  of 
the  foundation,  and  are  always  to  be  made  use  of  in  large  build- 
ings, and  in  walls  of  considerable  length. 

Lintel. — The  lintel,  or  beam,  extends  in  a  right  line  over  a 
vacant  space,  from  one  column  or  wall,  to  another.  The 
strength  of  the  lintel  will  be  greater  in  proportion  as  its  trans- 
verse vertical  diameter  exceeds  the  horizontal,  the  strength  be- 
ing always  as  the  square  of  the  depth.  [See  page  46].  The 
floor  is  the  lateral  continuation  or  connexion  of  beams  by  means 
of  a  covering  of  boards. 

Arch. — The  arch  is  a  transverse  member  of  a  building  an- 
swering the  same  purpose  as  the  lintel,  but  vastly  exceeding  it  in 
strength.  The  arch,  unlike  the  Hntel,  may  consist  of  any  num- 
ber of  constituent  pieces,  without  impairing  its  strength.  It  is, 
however,  necessary  that  all  the  pieces  should  possess  a  uniform 
shape,  the  shape  of  a  portion  of  a  wedge  ;  and  that  the  joints, 
formed  by  the  contact  of  their  surfaces,  should  point  towards  a 
<)ommon  centre.  In  this  case,  no  one  portion  of  the  arch  can 
be  displaced  or  forced  imvard  ;  and  the  arch  cannot  be  broken 
by  any  force  which  is  not  sufhcient  to  crush  the  materials  of 
which  it  is  made.  In  arches  made  of  common  bricks,  the  sides 
of  which  are  parallel,  any  one  of  the  bricks  might  be  forced  in- 
ward, were  it  not  for  the  adhesion  of  the  cement.  Any  two  of 
the  bricks  however,  constitute  a  wedge,  by  the  disposition  of 
their  mortar,  and  cannot  collectively  be  forced  inward.  An 
arch  of  the  proper  form,  when  complete,  is  rendered  stronger, 
instead  of  weaker,  by  the  pressure  of  a  considerable  w^eight, 
provided  this  pressure  be  uniform.  [PI.  I.  Fig.  k'].  While 
building,  however,  it  requires  to  be  supported  by  a  centring  of 
the  shape  of  its  internal  surface,  until  it  is  complete.  The  up- 
per stone  of  an  arch  is  called  the  key  stone,  but  is  not  more  es- 
sential than  any  other. 


OF   ARCHITECTURE   AND  BUILDING. 


119 


In  regard  to  the  shape  of  the  arch,  its  most  simple  form  is  that 
of  the  semi-circle.  [PI.  I.  Fig.  k~\.  It  is,  however,  very  fre- 
quently a  smaller  arc  of  a  circle,  and  still  more  frequently  a  por- 
tion of  an  ellipse.  The  simplest  theory  of  an  arch  supporting  it- 
self only,  is  that  of  Dr  Hooke.  The  arch,  when  it  has  only  its 
own  weight  to  bear,  may  be  considered  as  the  inversion  of  a  chain, 
suspended  at  each  end.  The  chain  hangs  in  such  a  form,  that 
the  weight  of  each  link  or  portion  is  held  in  equilibrium  by  the 
result  of  two  forces  acting  at  its  extremities  ;  and  these  forces, 
or  tensions,  are  produced,  the  one  by  the  weight  of  the  portion 
of  the  chain  below  the  link,  the  other  by  the  same  weight  in- 
creased by  that  of  the  hnk  itself,  both  of  them  acting  originally 
in  a  vertical  direction.  Now  supposing  the  chain  inverted,  so 
as  to  constitute  an  arch  of  the  same  form  and  weight,  the  rela- 
tive situations  of  the  forces  wall  be  the  same,  only  they  will  act 
in  contrary  directions,  so  that  they  are  compounded  in  a  similar 
manner,  and  balance  each  other  on  the  same  conditions.  The 
arch  thus  formed,  is  denominated  a  catenary  arch.  [PI.  1.  Fig.  T], 
In  common  cases  it  differs  but  little  from  a  circular  arch  of  the 
extent  of  about  one  third  of  a  whole  circle,  and  rising  from  the 
abutments  with  an  obliquity  of  about  30  degrees  from  a  per- 
pendicular. 

But  though  the  catenary  arch  is  the  best  form  for  supporting 
its  own  weight,  and  also  all  additional  weight  which  presses  in 
a  vertical  direction,  it  is  not  the  best  form  to  resist  lateral  pres- 
sure, or  pressure  like  that  of  fluids,  acting  equally  in  all  direc- 
tions. Thus  the  arches  of  bridges  and  similar  structures, 
when  covered  with  loose  stones  and  earth,  are  pressed  side- 
ways, as  well  as  vertically,  in  the  same  manner  as  if  they  sup- 
ported a  weight  of  fluid.  In  this  case,  it  is  necessary  that  the 
arch  should  arise  more  perpendicularly  from  the  abutment,  and 
that  its  general  figure  should  be  that  of  the  longitudinal  segment 
of  an  ellipse.  [PI.  I.  Fig.  m].  In  small  arches  in  common 
buildings,  w^here  the  disturbing  force  is  not  great,  it  is  of  little 
consequence  what  is  the  shape  of  the  curve.  The  outlines 
may  even  be  perfecdy  straight,  as  in  the  tier  of  bricks  which 


120  OF  ARCHITECTURE   AND  BUILDING. 

we  frequently  see  over  a  window.  This  is,  strictly  speaking,  a 
real  arch,  provided  the  surfaces  of  the  bricks  tend  towards  a 
common  centre.  [PI.  I.  Fig.  5].  It  is  the  weakest  kind  of 
arch,  and  a  part  of  it  is  necessarily  superfluous,  since  no  great- 
er portion  can  act  in  supporting  a  weight  above  it,  than  can 
be  included  between  two  curved  or  arched  lines. 

Besides  the  arches  already  mentioned,  various  others  are  in 
use.  The  acute  or  lancet  arch,  [PI.  I.  Fig.  0]  much  used  in 
Gothic  architecture,  is  described  usually  from  two  centres  out- 
side the  arch.  It  is  a  strong  arch  for  supporting  vertical  pres- 
sure. The  rampant  arch  [Fig.  n\  is  one,  in  which  the  two  ends 
spring  from  unequal  heights.  The  horse  shoe  or  Moorish  arch 
[Fig.  p  and  q\  is  described  from  one  or  more  centres  placed 
above  the  base  line.  In  this  arch,  the  lower  parts  are  in  dan- 
ger of  being  forced  inward.  The  ogee  arch  [Fig.  r]  is  conca- 
vo-convex, and  therefore  fit  only  for  ornament. 

In  describing  arches,  the  upper  surface  is  called  the  extrados, 
and  the  inner,  the  intrados.  The  springing  lines  are  those 
where  the  intrados  meets  the  abutments,  or  supporting  walls. 
The  span  is  the  distance  from  one  springing  line  to  the  other. 
The  wedge-shaped  stones  which  form  an  arch,  are  sometimes 
called  voussoirs,  the  uppermost  being  the  key  stone.  [PI.  I. 
Fig.  The  part  of  a  pier  from  which  an  arch  springs,  is 
called  the  impost,  and  the  curve  formed  by  the  upper  side  of 
the  voussoirs,  the  archivolt. 

Abutments. — It  is  necessary  that  the  walls,  abutments,  and 
piers,  on  which  arches  are  supported,  should  be  so  firm  as  to 
resist  the  lateral  thrust,  as  well  as  vertical  pressure,  of  the  arch. 
It  will  at  once  be  seen  that  the  lateral  or  sideway  pressure  of 
an  arch  is  very  considerable,  when  we  recollect  that  every  stone, 
or  portion  of  the  arch,  is  a  wedge,  a  part  of  whose  force  acts 
to  separate  the  abutments.  For  want  of  attention  to  this  cir- 
cumstance, important  mistakes  have  been  committed,  the 
strength  of  buildings  materially  impaired,  and  their  ruin  accel- 
erated. In  some  cases,  the  want  of  lateral  firmness  in  the 
walls,  is  compensated  by  a  bar  of  iron  stretched  across  the  span 


OF  ARCHITECTURE  AND  BUILDING. 


121 


of  the  arch  and  connecting  the  abutments,  like  the  tie  beam  of 
a  roof.  This  is  the  case  in  the  cathedral  of  Milan,  and  some 
other  Gothic  buildings.  ^ 

Arcade. — In  an  arcade,  or  continuation  of  arches,  it  is  only- 
necessary  that  the  outer  supports  of  the  terminal  arches  should 
be  strong  enough  to  resist  horizontal  pressure.  In  the  inter- 
mediate arches,  the  lateral-  force  of  each  arch  is  counteracted 
by  the  opposing  lateral  force  of  the  one  contiguous  to  it.  In 
bridges,  however,  where  individual  arches  are  Hable  to  be  de- 
stroyed by  accident,  it  is  desirable,  that  each  of  the  piers  should 
possess  sufficient  horizontal  strength,  to  resist  the  lateral  pres- 
sure of  the  adjoining  arches. 

Vault. — The  vaiilt  is  the  lateral  continuation  of  an  arch, 
serving  to  cover  an  area,  or  passage,  and  bearing  the  same  rela- 
tion to  the  arch,  that  the  wall  does  to  the  column.  A  simple 
vault  is  constructed  on  the  principles  of  the  arch,  and  distrib- 
utes its  pressure  equally  along  the  walls,  or  abutments.  A  com- 
plex or  groined  vault  is  made  by  two  vaults  intersecting  each 
other,  in  which  case,  the  pressure  is  thrown  upon  springing 
points,  and  is  greatly  increased  at  those  points.  The  groined 
vault  is  common  in  Gothic  architecture.    [PI.  VI.  Fig.  6]. 

Dome. — The  dome,  sometimes  called  cupola,  is  a  concave 
covering  to  a  building,  or  part  of  it,  and  may  be  either  a  seg- 
ment of  a  sphere,  of  a  spheroid,  or  of  any  similar  figure. 
When  built  of  stone,  it  is  a  very  strong  kind  of  structure,  even 
more  so  than  the  arch,  since  the  tendency  of  each  part  to  fall, 
is  counteracted,  not  only  by  those  above  and  below  it,  but  also 
by  those  on  each  side.  It  is  only  necessary  that  the  constituent 
pieces  should  have  a  common  form,  and  that  this  form  should 
be  somewhat  like  the  frustum  of  a  pyramid,  so  that  when  placed 
in  its  situation,  its  four  angles  may  point  toward  the  centre,  or 
axis,  of  the  dome.  During  the  erection  of  a  dome,  it  is  not 
necessary  that  it  should  be  supported  by  a  centring,  until  com- 
plete, as  is  done  in  the  arch.    Each  circle  of  stones,  when 

*  Cadell's  Journey  through  Carniola  and  Italy,  vol.  ii.  p.  77. 

16 


122 


OF  ARCHITECTURE  AND  BUILDING. 


laid,  is  capable  of  supporting  itself,  without  aid  from  those 
above  it.  It  follows  that  the  dome  may  be  left  open  at  top, 
without  a  key  stone,  and  yet  be  perfectly  secure,  in  this  respect, 
being  the  reverse  of  the  arch.  The  dome  of  the  Pantheon, 
at  Rome,  has  been  always  open  at  top,  and  yet  has  stood  unim- 
paired for  nearly  2000  years.  The  upper  circle  of  stones, 
though  apparently  the  w^eakest,  is  nevertheless  often  made  to 
support  the  additional  weight  of  a  lantern  or  tower  above  it. 
In  several  of  the  largest  cathedrals,  there  are  two  domes,  one 
within  the  other,  which  contribute  their  joint  support  to  the  lan- 
tern which  rests  upon  the  top.  In  these  buildings,  the  dome 
rests  upon  a  circular  wall,  which  is  supported  in  its  turn  by 
arches  upon  massive  pillars  or  piers.  This  construction  is  cal- 
led building  upon  pendentives,  and  gives  open  space  and  room 
for  passage,  beneath  the  dome. 

The  remarks  which  have  been  made  in  regard  to  the  abut- 
ments of  the  arch,  apply  equally  to  the  walls  immediately  sup- 
porting a  dome.  They  must  be  of  sufficient  thickness  and 
solidity  to  resist  the  lateral  pressure  of  the  dome,  which  is  very 
great.  The  walls  of  the  Roman  Pantheon  are  of  great  deptli 
and  solidity.  In  order  that  a  dome  in  itself  should  be  perfect- 
ly secure,  its  lower  parts  must  not  be  too  nearly  vertical,  since 
in  this  case,  they  partake  of  the  nature  of  perpendicular  walls, 
and  are  acted  upon  by  the  spreading  force  of  the  parts  above 
them.  The  dome  of  St  Paul's  church,  in  London,  and  some 
others  of  similar  construction,  are  bound  with  chains  or  hoops 
of  iron  to  prevent  them  from  spreading  at  bottom.  Domes 
which  are  made  of  wood,  depend  in  part  for  their  strength, 
on  their  internal  carpentry.  The  Halle  du  Bled,  in  Paris, 
had,  originally,  a  wooden  dome  more  than  200  feet  in  diam- 
eter, and  only  one  foot  in  thickness.  This  has  since  been 
replaced  by  a  dome  of  iron. 

Plate  I. — In  the  first  plate  is  given  a  comparative  view  in 
outline  of  some  of  the  most  remarkable  domes  in  ancient  and 
modern  buildings,  together  with  the  edifices  to  which  they  be- 
long, likewise  various  other  structures  reduced  to  the  same  scale. 


OF  ARCHITECTURE  AND  BUILDING. 


123 


The  highest  dome,  [No.  3]  is  that  of  St  Peter's  church,  at 
Rome,  generally  considered  the  most  splendid  building  in  the 
world,  and  one  of  the  largest  in  size.  This  edifice  was  a  cen- 
tury in  building,  from  about  1510  to  1610.  It  was  begun  by 
Bramante,  and  finished  by  Michael  Angelo,  and  Vignola.  The 
dome  is  of  an  ellipsoidal  form,  solid  at  bottom,  but  divided  into 
two  thin,  concentric  domes  at  top,  between  which  is  the  stair 
leading  to  the  lantern.  The  whole  height  from  the  ground  to 
the  cross  at  top,  is  about  470  feet.  The  base  of  the  dome  rests 
upon  arches,  supported  by  massive  stone  piers.  Widiin  the  last 
century,  some  fissures  of  dangerous  appearance  were  discovered 
in  this  dome,  to  remedy  which,  it  was  surrounded  with  iron 
chains  by  the  artist  Zabaglia. 

The  next  dome  in  height,  [No.  4]  is  that  of  the  church  of  St 
Maria  del  Fiore,  at  Florence.  Its  vertical  section  is  an  elon- 
gated ellipsoid,  its  horizontal  section  octagonal.  This  church 
is  about  380  feet  high,  and  was  built  between  1298  and  1472. 
The  dome  was  erected  by  Bruneleschi,  one  of  the  earliest  re- 
vivers of  antique  architecture. 

St  Paul's  cathedral,  London,  [No.  5]  was  erected  by  Sir 
Christopher  Wren,  between  1685  and  1710.  It  has  two  domes 
at  different  heights,  the  inner  being  made  of  brick,  and  the  out- 
er of  wood.  Between  the  two,  is  a  hollow,  truncated  cone  of 
brick  work,  which  furnishes  the  support  of  the  lantern  at  top. 
The  outline  of  the  dome  is  somewhat  more  than  a  semicircle, 
and  is  prevented  from  spreading  at  bottom,  by  a  strong  iron 
hoop. 

The  church  of  St  Genevieve,  in  Paris,  [No.  6]  which,  dur- 
ing the  absence  of  the  Bourbon  family,  was  called  the  Panthe- 
on, was  begun  by  Soufflot,  in  1757.  This  edifice  has  been 
threatened  with  ruin  in  consequence  of  the  piers,  which  support 
the  dome,  being  made  too  small  for  the  nature  of  the  material, 
and  the  superincumbent  weight.  It  became  necessary  to  re- 
place a  part  of  the  stones  which  were  crushed,  and  to  increase 
the  amount  of  support,  to  obtain  present  security. 


124 


OF  ARCHITECTURE  AND  BUILDING. 


The  Mosque  of  St  Sophia,  at  Constantinople,  [No.  7]  pre- 
sents a  specimen  of  the  kind  of  dome  used  by  the  ancients, 
which  was  more  flat  than  any  of  the  preceding  examples,  and 
was  usually  a  small  segment  of  a  sphere.  This  edifice  was 
erected  during  the  reign  of  Justinian,  in  the  sixth  century. 
Owing  to  the  want  of  sufficient  solidity  in  the  supporting  wall, 
the  dome  fell  down  at  two  successive  times,  and  the  architect 
was  under  the  necessity  of  filling  up  the  subjacent  arcades,  and 
of  building  large  buttresses  on  the  outside  of  the  wall,  to  resist 
the  pressure,  and  give  to  the  dome  eventual  stability.  The 
span  of  this  dome  is  112  feet. 

The  Pantheon,  at  Rome,  [No.  8]  is  probably  the  oldest 
dome  now  standing,  and  is  one  of  the  best  constructed.  Its 
outer  and  inner  surfaces  are  of  different  curvatures,  so  that  the 
thickness  increases  downward,  the  inner  surface  being  a  hemi- 
sphere. The  walls  of  this  edifice  are  of  great  solidity,  and  to 
this  circumstance  the  security  of  the  superstructure  is  in  part 
owing.  This  dome  is  open  at  the  top.  It  was  built  by  Agrip- 
pa,  in  the  reign  of  Augustus  Caesar.  A  more  perfect  view  of 
the  Pantheon,  is  given  in  Plate  V. 

The  outline  of  St  Mark's  church,  at  Venice,  which  has  sev- 
eral domes ;  that  of  the  front  of  the  Parthenon,  at  Athens, 
which  shows  the  lowness  of  the  Grecian  pediment ;  that  of  the 
restored  temple  of  Vesta,  at  Tivoli,  and  lastly  that  of  the  small 
Ionic  temple  which  stood  upon  the  Ilissus,  are  added  merely 
to  give  an  idea  of  their  comparative  size.  The  column  erected 
to  the  memory  of  the  emperor  Trajan,  also  one  of  the  obelisks 
brought  from  Egypt  by  the  ancient  Romans,  are  introduced 
upon  the  same  scale. 

No.  1,  in  the  same  plate,  represents  the  outline  of  the  largest 
of  the  Egyptian  Pyramids,  respecting  the  dimensions  of  which, 
travellers  vary  greatly  in  their  accounts.  One  of  the  more 
moderate  of  their  estimates  is  here  taken,  which  makes  the 
height  a  little  less  than  500  feet. 

No.  2,  shows  the  length  and  height  of  the  CoHseum,  at  Rome 
a  vast  elliptical  amphitheatre,  which  15,000  men  were  occupied 


OF  ARCHITECTURE  AND  BUILDING. 


125 


ten  years  in  completing.  It  was  built  in  the  reign  of  Vespasian 
and  Titus,  and  its  walls  are  standing  at  the  present  day. 

No.  15,  represents  the  celebrated  leaning  tower  of  Pisa. 
The  several  stories  of  this  structure,  are  supported  by  arcades 
upon  columns,  in  the  Greco-gothic  style.  The  height  of  the 
whole  is  180  feet.  This  lower  leans  over  about  14  feet  from 
a  perpendicular.  The  view  here  taken  of  it,  does  not  represent  its 
greatest  inclination.  Whether  the  obliquity  was  the  effect  of 
design,  or  of  the  settling  of  the  foundation  on  one  side,  is  a 
point  upon  which  writers  are  not  agreed.  It  was  built  in  the 
twelfth  century. 

No.  16,  is  the  steeple  of  the  Gothic  Cathedral,  at  Strasburg. 
It  is  among  the  highest  steeples  in  Europe,  and  is  introduced 
to  show  its  comparative  elevation.  No.  17,  is  the  centre  steeple 
of  the  Duomo  or  Cathedral  of  Milan,  about  350  feet  high. 
This  edifice  is  of  white  marble.  Its  general  character  is  Goth- 
ic, intermixed  with  details  in  the  later  Roman  style. 

The  proportions  of  most  of  the  foregoing  buildings  are  taken 
from  Durand,  who  has  reduced  them  to  a  scale.  The  same 
scale  applies  to  the  other  architectural  plates  in  this  volume, 
with  the  exception  of  perspective  representations,  in  which  more 
than  one  side  is  seen. 

The  outlines  of  several  American  edifices,  reduced  to  the 
same  scale,  are  added  in  this  plate  for  the  convenience 
of  comparison.  No.  18,  is  that  of  the  Capitol,  at  Washington, 
built  of  freestone,  the  length  of  which  is  350  feet,  the  height 
of  the  front  70  feet,  and  the  height  of  the  centre  dome  120 
feet.  No.  19,  is  the  City  Hall,  at  New  York,  built  chiefly  of 
marble,  its  length  220  feet,  and  the  height  of  the  statue  at  top, 
120  feet.  No.  20,  is  the  State  House,  Boston,  173  feet  in 
length,  built  of  brick,  and  painted.  No.  21,  is  the  Bank 
of  the  United  States,  at  Philadelphia,  a  marble  building,  having 
its  front  86  feet  wide,  copied  in  most  respects  from  the  Parthe- 
non at  Athens.  No.  22,  the  monument  erected  at  Baltimore, 
in  commemoration  of  the  battle  and  victory  at  that  place. 
Height  about  55  feet. 


/ 


126  OF  ARCHITECTURE   AND  BUILDING. 

Ttoof. — The  roof  is  the  most  common  and  cheap  method  of 
covering  buildings,  to  protect  them  from  rain  and  other  effects 
of  the  weather.  It  is  sometimes  flat,  but  more  frequently  ob- 
lique in  its  shape.  The  flat  or  platform  roof  is  the  least  advan- 
tageous for  shedding  rain,  and  is  seldom  used  in  northern  coun- 
tries. The  pe7it  roof,  consisting  of  two  oblique  sides  meeting 
at  top,  is  the  most  common  form  [PL  I.  Fig.  lo].  These  roofs 
are  made  steepest  in  cold  climates,  where  they  are  liable 
to  be  loaded  with  snow.  Where  the  four  sides  of  the 
roof  are  all  oblique,  it  is  denominated  a  hipped  roof,  [Fig.  x\ 
and  where  there  are  two  portions  to  the  roof,  of  different  obli- 
quity, it  is  a  curb,  or  mansard  roof.  [Fig.  y\.  In  modern 
times,  roofs  are  made  almost  exclusively  of  wood,  though  fre- 
quently covered  with  incombustible  materials.  The  internal 
structure  or  carpentry  of  roofs,  is  a  subject  of  considerable  me- 
chanical contrivance.  The  roof  is  supported  by  rafters  which 
abut  on  the  walls  on  each  side,  hke  the  extremities  of  an  arch. 
If  no  other  timbers  existed,  except  the  rafters,  they  would  exert 
a  strong  lateral  pressure  on  the  walls,  tending  to  separate  and  over- 
throw them.  *  To  counteract  this  lateral  force,  a  tie  beam,  as  it 
is  called,  extends  across,  receiving  the  ends  of  the  rafters,  and  pro- 
tecting the  wall  from  their  horizontal  thrust.  To  prevent  the  tie 
beam  from  sagging,  or  bending  downward  with  its  own  weight,  a 
king  post  is  erected  from  this  beam,  to  the  upper  angle  of  the 
rafters,  serving  to  connect  the  whole,  and  to  suspend  the  weight 
of  the  beam.  This  is  called  trussing,  (^ueen  posts  are  some- 
times added,  parallel  to  the  king  post,  in  large  roofs,  also  vari- 
ous other  connecting  timbers.  In  Gothic  buildings,  where  the 
vauhs  do  not  admit  of  the  use  of  a  tie  beam,  the  rafters  are 
prevented  from  spreading,  as  in  an  arch,  by  the  strength  of  the 
buttresses. 

*  The  largest  roof  that  has  hitherto  been  built,  is  supposed  to  have  been  that 
of  the  riding  house,  at  Moscow.  Its  span  was  235  feet,  and  the  slope  of  the 
roof,  about  19  degrees.  The  principal  support  of  this  immense  truss,  consist- 
ed in  an  arch  of  timber  in  three  thicknesses,  indented  together,  and  strapped 
and  bolted  with  iron.  The  principal  rafters  and  tie  beams,  were  supported  by 
several  vertical  pieces,  notched  to  this  arch,  and  the  whole  stiffened  by  diago- 
nal braces.    Tredgold's  Carpentry,  p.  87. 


OF  ARCHITECTURE   AND  BUILDING. 


127 


In  comparing  the  lateral  pressure  of  a  high  roof,  with  that 
of  a  low  one,  the  length  of  the  tie  beam  being  the  same,  it  will 
be  seen  that  a  high  roof,  from  its  containing  most  materials,  will 
produce  the  greatest  pressure,  as  far  as  weight  is  concerned. 
On  the  other  hand,  if  the  weight  of  both  be  equal,  then  the 
low  roof  will  exert  the  greater  pressure,  and  this  will  increase  in 
proportion  to  the  distance  of  the  point  at  which  perpendiculars 
drawn  from  the  end  of  each  rafter,  would  meet. 

In  roofs,  as  well  as  in  wooden  domes,  and  bridges,  the  mate- 
rials are  subjected  to  an  internal  strain,  to  resist  which,  the  co- 
hesive strength  of  the  material  is  relied  on.  On  this  account, 
beams  should,  when  possible,  be  of  one  piece.  Where  this 
cannot  be  effected,  two  or  more  beams  are  connected  together 
by  splicing.  Spliced  beams  are  never  so  strong  as  whole  ones, 
yet  they  may  be  made  to  approach  the  same  strength,  by  affix- 
ing lateral  pieces,  or  by  making  the  ends  overlay  each  other, 
and  connecting  them  with  bolts  and  straps  of  iron.  The  ten- 
dency to  separate  is  also  resisted,  by  letting  the  two  pieces  into 
each  other,  by  the  process  called  scarfing.  Mortises,  intended 
to  truss  or  suspend  one  piece  by  another,  should  be  formed 
upon  similar  principles. 

Roofs  in  this  country,  after  being  boarded,  receive  a  second- 
ary covering  of  shingles.  When  intended  to  be  incombustible, 
they  are  covered  with  slates  or  earthen  tiles,  or  with  sheets  of 
lead,  copper,  or  tinned  iron.  Slates  are  preferable  to  tiles,  be- 
ing lighter,  and  absorbing  less  moisture.  Metallic  sheets  are 
chiefly  used  for  flat  roofs,  wooden  domes,  and  curved  and  an- 
gular surfaces,  which  require  a  flexible  material  to  cover  them, 
or  have  not  a  sufficient  pitch  to  shed  the  rain  from  slates  or 
shingles.  Various  artificial  compositions  are  occasionally  used 
to  cover  roofs,  the  most  common  of  which,  are  mixtures  of  tar 
with  lime,  and  sometimes  with  sand  and  gravel.  ♦ 

Styles  of  Building. — The  architecture  of  different  countries, 
has  been  characterized  by  peculiarities  in  external  form,  and  in 
modes  of  construction.  These  peculiarities,  among  ancient 
nations,  were  so  distinct,  that  their  structures  may  be  identified 


128 


OF  ARCHITECTURE  AND  BUILDING. 


even  in  the  state  of  ruins  ;  and  the  origin  and  era  of  each  may- 
be conjectured  with  tolerable  accuracy.  Before  we  proceed 
to  describe  architectural  objects,  it  is  necessary  to  explain 
certain  terms,  which  are  used  to  denote  their  different 
constituent  portions.  The  architectural  orders  will  be  spoken 
of  under  the  head  of  the  Grecian  and  Roman  styles,  but  their 
component  parts  ought  previously  to  be  understood. 

Definitions. — The  front  or  facade  of  a  building,  made  after 
the  ancient  models,  or  any  portion  of  it,  may  present  three  parts, 
occupying  different  heights. 

The  pedestal  is  the  lower  part,  usually  supporting  a  column. 
The  single  pedestal  is  wanting  in  most  antique  structures,  and 
its  place  supplied  by  a  stylohate.  The  stylobate  is  either  a 
platform  with  steps,  or  a  continuous  pedestal,  supporting  a  row  of 
columns.  The  lower  part  of  a  finished  pedestal  is  called  the 
plinth^  ^  the  middle  part  is  the  die,  and  the  upper  part  the  cornice 
of  the  pedestal,  or  surbase. 

The  column,  is  the  middle  part,  situated  upon  the  pedestal  or 
stylobate.  It  is  commonly  detached  from  the  wall,  but  is  some- 
times buried  in  it  for  half  its  diameter,  and  is  then  said  to  be 
engaged.  Pilasters  are  square  or  flat  columns,  attached  to 
walls.  The  lower  part  of  a  column,  when  distinct,  is  called 
the  base;  the  middle,  or  longest  part,  is  the  shaft,  and  the  upper, 
or  ornamented  part,  is  the  capital.  The  height  of  columns  is 
measured  in  diameters  of  the  column  itself,  taken  always  at 
the  base. 

The  entablature,  is  the  horizontal,  continuous  portion,  which 
rests  upon  the  top  of  a  row  of  columns.  The  lower  part  of 
the  entablature  is  called  the  architrave,  or  epistylium.  The 
middle  part  is  the  frieze,  which,  from  its  usually  containing 
sculpture,  was  called  zophorus  by  the  ancients.  The  upper,  or 
projecting  part,  is  the  cornice. 

*  The  name  plinth,  in  its  general  sense,  is  applied  to  any  square  projecting 
basis,  such  as  those  at  the  bottom  of  walls,  and  under  the  base  of  columns. 


OF   ARCHITECTURE   AND  BUILDING. 


129 


Stylobate  or 
Pedestal  i 


Base. 
Cornice. 

Die. 


Plinth. 


A  pediment,  is  the  triangular  face,  produced  by  the  extremi- 
ty of  a  roof.  The  middle,  or  flat  portion,  inclosed  by  the  cor- 
nice of  the  pediment,  is  called  the  tympanum.  Pedestals  for 
statues,  erected  on  the  summit  and  extremities  of  a  pediment, 
are  called  acroteria  [PI.  V.  Fig.  2].  An  attic,  is  an  upper 
part  of  a  building,  terminated  at  top  by  a  horizontal  line,  in- 
stead of  a  pediment. 

The  different  mouldings  in  architecture  are  described  from 
their  sections,  or  from  the  profile  which  they  present,  when  cut 
across.  Of  these  the  torus  is  a  convert  moulding,  the  section 
of  which  is  a  semicircle  or  nearly  so  [PI.  I.  Fig.  a].  The 
astragal,  is  like  the  torus,  but  smaller  [Fig.  b].  The  ovolo 
17 


130 


OF  ARCHITECTURE   AND  BUILDING. 


is  convex,  but  its  outline  is  only  the  quarter  of  a  circle  [Fig. 
c].  The  echinus  resembles  the  ovolo,  but  its  outline  is  spiral, 
not  circular  [Fig.  d].  The  scotia  is  a  deep,  concave  mould- 
ing [Fig.  e].  The  cavetto  is  also  concave,  and  occupying 
but  a  quarter  of  a  circle  [Fig.  /].  The  cymatium  is  an  un- 
dulated-moulding, of  which  the  upper  part  is  concave,  and  the 
lower  convex  [Fig.  g~\.  The  ogee  or  talon,  is  an  inverted 
cymatium  [Fig.  A].  The  fillet  is  a  small  square  or  flat 
moulding  [Fig.  {]. 

JVLeasures. — In  architectural  measurement,  a  diameter  means 
the  width  of  a  column  at  the  base.  A  module  is  half  a  diam- 
eter.   A  minute  is  a  sixtieth  part  of  a  diameter. 

Drawings. — In  representing  edifices  by  drawings,  architects 
make  use  of  the  plan,  elevation,  section,  and  'perspective.  The 
plan  is  a  map,  or  design,  of  a  horizontal  surface,  showing  the 
ichnographic  projection,  or  ground  work,  with  the  relative  po- 
sition of  walls,  columns,  doors,  &ic.  f  The  elevation  is  the  or- 
thographic projection  of  a  front,  or  vertical  surface ;  this  being 
represented,  not  as  it  is  actually  seen  in  perspective,  but  as  it 
would  appear  if  seen  from  an  infinite  distance.  The  section 
shows  the  interior  of  a  building,  supposing  the  part  in  front  of 
an  intersecting  plane,  to  be  removed.  The  perspective  shows 
the  building  as  it  actually  appears  to  the  eye,  subject  to  the  laws 
of  scenographic  perspective.  .  The  three  former  are  used  by 
architects,  for  purposes  of  admeasurement,  the  latter  is  used 
also  by  painters,  and  is  capable  of  bringing  more  than  one  side 
into  the  same  view,  as  the  eye  actually  perceives  them. 

Restorations. — As  the  most  approved  features  in  modern 
architecture,  are  derived  from  buildings  which  are  more  or  less 
ancient,  and  as  many  of  these  buildings  are  now  in  too  dilapi- 
dated a  state  to  be  easily  copied,  recourse  is  had  to  such  imi- 
tative restorations  in  drawings  and  models,  as  can  be  made  out 

*  By  a  singular  mixture  of  derivations,  the  Greek,  Latin,  Italian,  French, 
and  English  languages  are  laid  under  contribution  for  the  technical  terms  of 
Architecture. 

t  See  various  plans  of  temples  on  pages  136,  137. 


OF  ARCHITECTURE   AND  liUILDlNG. 


131 


from  the  fragments  and  ruins  which  remain.  In  consequence 
of  the  known  simplicity  and  regularity  of  most  antique  edifices, 
the  task  of  restoration  is  less  difficult  than  might  be  supposed. 
The  ground  work,  which  is  commonly  extant,  shows  the  length 
and  breadth  of  the  building,  with  the  position  of  its  walls,  doors, 
and  columns.  A  single  column,  whether  standing  or  fallen, 
and  a  fragment  of  the  entablature,  furnish  data  from  which  the 
remainder  of  the  colonnade,  and  the  height  of  the  main  body, 
can  be  made  out.  A  single  stone  from  the  cornice  of  the  pedi- 
ment, is  often  sufficient  to  give  the  angle  of  inclination,  and 
consequently  the  height  of  the  roof.  In  this  way,  beautiful 
restorations  are  obtained  of  structures,  when  in  so  ruinous  a 
state,  as  scarcely  to  have  left  one  stone  upon  another. 


EGYPTIAN  STYLE. 

In  ancient  Egypt,  a  style  of  building  prevailed,  more  mas- 
sive and  substantial  than  any  which  has  succeeded  it.  The 
elementary  features  of  Egyptian  architecture,  were  chiefly  as 
follows.  1.  Their  walls  were  of  great  thickness,  and  sloping 
on  the  outside.  This  feature  is  supposed  to  have  been  derived 
from'  the  mud  walls,  mounds,  and  caverns  of  their  ancestors. 
2.  The  roofs  and  covered  ways  were  flat,  or  without  pedi- 
ments, and  composed  of  blocks  of  stone,  reaching  from  one 
wall  or  column  to  another.  The  principle  of  the  arch,  although 
known  to  them,  was  seldom,  if  ever,  employed  by  them.  3. 
Their  columns  were  numerous,  close,  short,  and  very  large, 
being  sometimes  10  or  12  feet  in  diameter.  They  were  gener- 
ally without  bases,  and  had  a  great  variety  of  capitals,  from  a 
simple  square  block,  ornamented  with  hieroglyphics,  or  faces, 
to  an  elaborate  composition  of  palm  leaves  not  unlike  the  Co- 
rinthian capital.  4.  They  used  a  sort  of  concave  entablature, 
or  cornice,  composed  of  vertical  flutings,  or  leaves,  and  a  wing- 
ed globe  in  the  centre.  5.  Pyramids,  well  known  for  their 
prodigious  size,  and  obelisks  composed  of  a  single  stone,  often 
exceeding  70  feet  in  height,  are  structures  peculiarly  Egyptian. 


132 


OF  ARCHITECTURE  AND  BUILDING. 


6.  Statues  of  enormous  size,  sphinxes  carved  in  stone,  and 
sculptures  in  oudine  of  fabulous  deides  and  animals,  with  innu- 
merable hieroglyphics,  are  the  decoradve  objects  which  belong 
to  this  style  of  architecture. 

For  Egyptian  specimens,  see  PI.  I.  Fig.  1. ;  PI.  VI.  Fig. 
I,  and  PI.  VII.  Fig.  1,2,  and  3. 

The  architecture  of  the  ancient  Hindoos,  appears  to  have 
been  derived  from  the  same  original  ideas  as  the  Egyptian. 
The  most  remarkable  relics  of  this  people,  are  their  subterra- 
neous temples,  of  vast  size  and  elaborate^workmanship,  carved 
out  of  the  solid  rock,  at  Elephanta,  Ellora,  and  Salsette.  One 
of  their  columns  is  shown  in  Plate  VII.  Fig.  4. 

THE   CHINESE  STYLE. 

The  ancient  Tartars,  and  wandering  shepherds  of  Asia,  ap- 
pear to  have  lived  from  time  immemorial  in  tents,  a  kind  of 
habitation  adapted  to  their  erratic  life.  The  Chinese  have 
made  the  tent,  the  elementary  feature  of  their  architecture,  and 
of  their  style  any  one  may  form  an  idea,  by  inspecting  the  fig- 
ures which  are  depicted  upon  common  china  ware.  Chinese 
roofs  are  concave  on  the  upper  side,  as  if  made  of  canvass  in- 
stead of  wood.  A  Chinese  portico,  is  not  unlike  the  awnings 
spread  over  our  shop  windows  in  summer  time.  The  verandah, 
sometimes  copied  in  dwelling  houses  here,  is  a  structure  of  this 
sort.  The  Chinese  towers  and  pagodas,  have  concave  roofs, 
like  awnings,  projecting  over  their  several  stories.  The  light- 
ness of  the  style  used  by  the  Chinese,  leads  them  to  build  with 
wood,  sometimes  with  brick,  and  seldom  with  stone  [PI.  VI. 
Fig.  2,  and  VII.  Fig.  18]. 

THE  GRECIAN  STYLE. 

Grecian  architecture,  from  which  have  been  derived  the  most 
splendid  structures  of  later  ages,  has  its  origin  in  the  wooden 
hut  or  cabin,  formed  of  posts  set  in  the  earth,  and  covered  with 


OF  ARCHITECTURE  AND  BUILDING. 


133 


transverse  poles  and  rafters.  Its  beginnings  were  very  simple, 
being  little  more  than  imitations  in  stone,  of  the  original  posts 
and  beams.  By  degrees  these  were  modified  and  decorated, 
so  as  to  give  rise  to  the  distinction  of  what  are  now  called  the 
orders  of  architecture. 

Orders  of  Architecture. — By  the  architectural  orders,  are 
understood  certain  modes  of  proportioning  and  decorating  the 
column  and  its  entablature.  They  were  in  use  during  the  best 
days  of  Greece  and  Rome,  for  a  period  of  six  or  seven  centu- 
ries. They  were  lost  sight  of  in  the  dark  ages,  and  again  re- 
vived by  the  Italians  at  the  time  of  the  restoration  of  letters. 
The  Greeks  had  three  orders,  called  the  Doric,  Ionic,  and  Co- 
rinthian, These  were  adopted  and  modified  by  the  Romans, 
who  also  added  two  others,  called  the  Tuscan  and  Composite, 

Doric  Order. — The  Doric  is  the  earliest  and  most  massive 
order  of  the  Greeks.  It  is  known  by  its  large  columns  with 
plain  capitals ;  its  triglyphs  resembling  the  ends  of  beams,  and 
its  mutules  corresponding  to  those  of  rafters.  The  column,  in 
the  examples  at  Athens,  is  about  six  diameters  in  height.  In 
the  older  examples,  as  those  at  Paestum,  it  is  but  four  or  five. 
The  shaft  had  no  base,  but  stood  directly  on  the  stylobate.  It 
had  20  flutings,  which  were  superficial,  and  separated  by  angu- 
lar edges.  The  perpendicular  outline  was  nearly  straight. 
The  Doric  capital  was  plain,  being  formed  of  a  few  annulets  or 
rings,  a  large  echinus,  and  a  flat  stone  at  top  called  the  abacus. 
The  architrave  was  plain  ;  the  frieze  was  intersected  by  oblong 
projections  called  triglyphs,  divided  into  three  parts  by  vertical 
furrows,  and  ornamented  beneath,  by  guttcB  or  drops.  The 
spaces  between  the  triglyphs  were  called  metopes,  and  com- 
monly contained  sculptures.  The  sculptures  representing  Cen- 
taurs andLapithas,  carried  by  Lord  Elgin  to  London,  were  me- 
topes of  the  Parthenon,  or  temple  of  Minerva,  at  Athens.  The 
cornice  of  the  Doric  order  consisted  of  a  few  large  mouldings, 
having  on  their  under  side  a  series  of  square,  sloping  projec- 
tions, resembling  the  ends  of  rafters,  and  called  mutules. 
These  were  placed  over  both  triglyphs  and  metopes,  and  were 


134 


OF   ARCHITECTURE  AND  BUILDING. 


ornamented,  on  their  under  side,  with  circular  guttce.  The 
best  specimens  of  the  Doric  order,  are  found  in  the  Parthenon, 
the  Propylaea,  and  the  Temple  of  Theseus,  at  Athens  [PI. 

VI.  Fig.  7.  PL  IV.  Fig.  1,  2,  3,  4,  5,  and  6]. 

Ionic  Order. — The  Ionic  is  a  lighter  order  than  the  Doric, 
its  column  being  eight  or  nine  diameters  in  height.  It  had  a 
base  often  composed  of  a  torus,  a  scotia,  and  a  second  torus, 
with  intervening  fillets.    This  is  called  the  Attic  base  [PI. 

VII.  Fig.  9].  Others  were  used  in  different  parts  of  Greece. 
The  shaft  had  24,  or  more,  flutings,  which  were  narrow,  as 
deep  as  a  semicircle,  and  separated  by  a  fillet  or  square  edge. 
The  capital  of  this  order  consisted  of  two  parallel  double  scrolls, 
called  volutes,  occupying  opposite  sides,  and  supporting  an  ab- 
acus, which  was  nearly  square,  but  moulded  at  its  edges. 
These  volutes  have  been  considered  as  copied  from  ringlets  of 
hair,  or  perhaps  from  the  horns  of  Jupiter  Ammon.  When 
a  column  made  the  angle  of  an  edifice,  its  volutes  were  placed, 
not  upon  opposite,  but  on  contiguous  sides  ;  each  fronting  out- 
ward. In  this  case  the  volutes  interfered  ^vith  each  other  at 
the  corner,  and  were  obliged  to  assume  a  diagonal  direction. 
The  Ionic  entablature  consisted  of  an  architrave  and  frieze, 
which  were  continuous  or  unbroken,  and  a  cornice  of  various 
successive  mouldings,  at  the  lower  part  of  w^iich  was  often  a 
row  of  dentels  or  square  teeth.  The  examples  at  Athens,  of 
the  Ionic  order,  are  the  temple  of  Erectheus,  and  the  temple 
on  the  Ilissus,  which  was  standing  in  Stuart's  time  70  years 
since,  but  is  now  extinct  [PI.  VII.  Fig.  9.  PI.  IV.  Fig.  8, 
9,  10,  and  11. 

Corinthian  Order. — The  Corinthian  was  the  lightest  and 
most  decorated  of  the  Grecian  orders.  Its  base  resembled 
that  of  the  Ionic,  but  was  more  complicated.  The  shaft  was 
often  ten  diameters  in  height,  and  was  fluted  like  the  Ionic. 
The  capital  was  shaped  like  an  inverted  bell,  and  covered  on 
the  outside  with  tw^o  rows  of  leaves  of  the  plant  acanthus,  * 

*  The  origin  of  the  Corinthian  capital  has  heen  ascribed  to  the  sculptor  Cal- 
limachus,  who  is  said  to  have  copied  it  from  a  basket  accidentally  enveloped 


OF  ARCHITECTURE  AND  BUILDING. 


135 


above  which  were  eight  pairs  of  small  volutes.  Its  abacus  was 
moulded  and  concave  on  its  sides,  and  truncated  at  the  corners, 
with  a  flower  on  the  centre  of  each  side.  The  entablature  of 
the  Corinthian  order,  resembled  that  of  the  Ionic,  but  was  more 
complicated  and  ornamented,  and  had,  under  the  cornice,  a 
row  of  large  oblong  projections,  bearing  a  leaf  or  scroll  on  their 
under  side,  and  called  modillions.  No  vestiges  of  this  order  are 
now  found  in  the  remains  of  Corinth,  and  the  most  legitimate 
example  at  Athens,  is  in  the  choragic  monument  of  Lysicrates. 
The  Corinthian  order  was  much  employed  in  the  subsequent 
structures  of  Rome,  and  its  colonies  [PI.  VII.  Fig.  10.  PI. 
V.  Fig.  1,  2,  3,  &c]. 

Caryatides. — The  Greeks  sometimes  departed  so  far  from 
the  strict  use  of  the  orders,  as  to  introduce  statues,  in  the  place 
of  columns,  to  support  the  entablature.  Statues  of  slaves,  he- 
roes, and  gods,  appear  to  have  been  employed,  occasionally  for 
this  purpose.  The  principal  specimen  of  this  kind  of  architecture, 
which  remains,  is  in  a  portico,  called  Pandroseum,  attached  to 
the  temple  of  Erectheus,  at  Athens,  in  w^hich  statues  of  Carian 
females,  called  Caryatides,  are  substituted  for  columns  [PI. 
rV.  Fig.  9].    One  of  these  statues  has  been  carried  to  London. 

Grecian  Temple. — The  most  remarkable  public  edifices  of 
the  Greeks,  were  their  temples.  These  being  intended  as  pla- 
ces of  resort  for  the  priests,  rather  than  for  the  convening  of 
assemblies  within,  were  in  general  obscurely  lighted.  Their 
form  was  commonly  that  of  an  oblong  square,  having  a  colon- 
nade without,  and  a  walled  cell  within.  The  cell,  was  usually 
without  windows,  receiving  its  light  only  from  a  door  at  the  end, 
and  sometimes  from  an  opening  in  the  roof.  The  part  of  the 
colonnade  which  formed  the  front  portico,  was  called  the  pro- 
naos,  and  that  which  formed  the  back  part,  the  posticus.  The 
colonnade  was  subject  to  great  variety  in  the  number  and  dis- 
position of  its  columns,  from  which  Vitruvius  has  described  sev- 

in  leaves  of  acanthus.  A  more  probable  supposition  traces  its  origin  to  some 
of  the  Egyptian  capitals,  which  it  certainly  resembles. 


136 


OF  ARCHITECTURE   AND  BUILDING. 


en  different  species  of  temples.  These  were,  1.  The  temple 
with  antcR.  In  this  the  front  was  composed  of  pilasters,  call- 
ed antae,  on  the  sides,  and  two  columns  in  the  middle. 


2.  The  Prostyh 
only. 


This  had  a  row  of  columns  at  one  end 


3.  The  Amphiprostyle,  having  a  row  of  columns  at  each 


end. 


4.  The  Peripteral  temple.  This  was  surrounded  by  a  sin- 
gle row  of  columns,  having  six  in  front,  and  in  rear,  and  eleven 
counting  the  angular  columns,  on  each  side. 


ooooooooooo 

o   i  1   o 

'  o  o 
I    o  o 

o 


o  o  • 
o  o  I 

O 

ooooooooooo 


5.  The  Dipteral,  with  a  double  row  of  columns  all  round 
the  cell,  the  front  consisting  of  eight. 


OF   ARCHITFX'TURE   AND  BUILDING. 


137 


6.  The  Pseudo-dipteral  differs  from  the  dipteral,  in  having 
a  single  row  of  columns  on  the  sides,  at  the  same  distance  from 
the  cell,  as  if  the  temple  had  been  dipteral. 


ooooooooooooooo 

o    o 

o        I  \  o 

O  O       '  0  0 

0  0  ,00 

o        I  I  o 

o  o 
ooooooooooooooo 


7.  The  HypcRthral  temple  had  the  centre  of  its  roof  open  to 
the  sky.  It  was  colonnaded  without,  like  the  dipteral,  but  had 
ten  columns  in  front.  It  had  also  an  internal  colonnade,  called 
peristyle,  on  both  sides  of  the  open  space,  and  composed  of  two 
stories  or  colonnades,  one  above  the  other. 


ooooooooooooooooooo 
ooooooooooooooooooo 


o  o 
o  o  o 
o  o  o 


o  o 

o  o  o 

o  o  o 

o  o  o 

o  o  o 

O  O           '  '         o  o 

ooooooooooooooooooo 
ooooooooooooooooooo 


ooooooooo 


ooooooooo 


Temples,  especially  small  ones,  were  sometimes  made  of  a  cir- 
cular form.  When  these  were  wholly  open,  or  without  a  cell, 
they  were  called  Monopteral  temples.  When  there  was  a  cir- 
cular cell  within  the  colonnade,  they  were  called  Peripteral  * 

Grecian  Theatie. — The  theatre  of  the  Greeks,  which  was 
afterwards  copied  by  the  Romans,  was  built  in  the  form  of  a 
horse  shoe,  being  semicircular  on  one  side,  and  square  on  the 
other.  The  semicircular  part,  which  contained  the  audience, 
was  filled  with  concentric  seats,  ascending  from  the  centre,  to 

"  The  intercolumniation,  or  distance  between  the  columns,  according  to 
Vitruvius,  was  differently  arranged  under  the  following  names.  In  the  pyc- 
nostyle,  the  columns  were  a  diameter  and  a  half  apart.  In  the  systyle  they 
were  two  diameters  apart.  In  the  diastyle,  three.  In  the  araostyle,  more 
than  three.  In  the  eustyle,  two  and  a  quarter. 
18 


l'*^^  OF  ARCinTFXTURE   ANT)  BUILDING. 

the  outside.  In  the  middle,  or  bottom,  was  a  semicircular  floor 
called  the  orchestra.  The  opposite,  or  square  part,  contained 
the  actors.  Within  this  was  erected,  in  front  of  die  audience, 
a  wall  ornamented  with  columns  and  sculpture,  called  the  scena. 
The  stage,  or  floor,  between  this  part  and  the  orchestra,  was 
called  the  proscenium.  Upon  this  floor  was  often  erected  a 
moveable  wooden  stage,  called,  by  the  Romans,  pulpitum. 
The  ancient  theatre  was  open  to  the  sky,  but  a  temporary  awn- 
ing was  erected  to  shelter  the  audience  from  the  sun  and  rain. 

Remarks. — Grecian  architecture  is  considered  to  have  been 
in  its  greatest  perfection  in  the  age  of  Pericles  and  Phidias. 
The  sculpture  of  this  period,  is  admitted  to  have  been  superior 
to  that  of  any  other  age ;  and  although  architecture  is  a  more 
arbitrary  art,  than  sculpture,  yet  it  is  natural  to  conclude,  that 
the  state  of  things  which  gave  birth  to  excellence  in  the  one, 
must  have  produced  a  corresponding  power  of  conceiving  sub- 
limity and  beauty  in  the  other.  Grecian  architecture  was  in 
general,  distinguished  by  simplicity  of  structure,  fewness  of 
parts,  absence  of  arches,  lowness  of  pediments  and  roofs,  and 
by  decorative  curves,  the  outline  of  which  was  a  spiral  line,  or 
conic  section,  and  not  a  circular  arc,  as  afterwards  adopted  by 
the  Romans. 

Plate  IV. — This  plate  is  intended  to  give  a  view,  upon  the 
same  scale  as  PI.  1,  of  various  examples  of  Grecian  architec- 
ture, the  remains  of  which  are  extant  at  the  present  day.  The 
limits  of  the  plate  permit  only  the  front  elevation  to  be  given, 
which,  in  the  oblong  Grecian  temples,  was  the  end  of  the  build- 
ing. 

No.  1,  represents  the  principal  temple  at  Paestum,  in  Italy. 
At  this  place  are  now  standing,  the  walls  and  colonnades  of 
three  temples,  built  in  the  ancient  Doric  style,  and  undoubt- 
edly erected  by  a  Grecian  colony  in  that  country.  The 
characters  of  this  early  Doric,  are  short  and  heavy  columns 
much  diminished  upwards,  large  capitals,  and  a  massive  entab- 
lature, nearly  half  as  high  as  the  columns.    The  outline  of  the 


OP  ARCHITECTURE   AND  BUILDING. 


139 


columns  in  this  building  is  straight,  or  without  entasis.  The 
temple  appears  to  have  been  hypaethral,  though  the  number  of 
columns  is  less  than  in  the  rule  prescribed  by  Vitruvius. 

No.  2,  is  the  Temple  of  Concord,  commonly  so  called,  at 
Agrigentum,  now  Girgenti,  in  Sicily.  It  is  erected  in  the  mas- 
sive style  of  the  older  Doric,  on  a  stylobate  of  four  steps,  and, 
with  the  exception  of  the  roof,  is  in  a  state  of  good  preservation 
at  the  present  day.  Other  Doric  ruins  are  found  in  the  same 
place,  also  at  Segesta,  Selinus,  and  other  parts  of  Sicily. 
Views  of  these  structures  are  given  in  Wilkins's  Magna  Grcecia, 

No.  3,  is  the  Temple  of  Theseus,  at  Athens,  situated  in  the 
lower  part  of  that  city,  some  way  from  the  Acropolis.  It  is  the 
most  perfectly  preserved  of  any  of  the  Athenian  edifices,  its 
columns  and  walls  having  suffered  scarce  any  dilapidation.  At 
the  top  of  its  stone  platform,  or  stylobate,  it  measures  104  feet 
in  length,  by  45  in  breadth,  and  has  six  columns  on  each  front, 
with  thirteen  on  each  side,  counting  those  at  the  angles.  The 
temple  of  Theseus  was  erected  by  Cimon,  the  son  of  Miltiades, 
about  450  years  before  Christ.  The  sculptures  upon  the  frieze 
of  this  building,  are  supposed  by  Stuart,  and  others,  to  refer  to 
the  exploits  of  Theseus,  but  according  to  Mr  Wilkins,  they 
represent  the  labors  of  Hercules. 

No.  4,  is  the  Propylaea,  at  Athens,  a  structure  of  much 
beauty,  which  commanded  the  entrance  to  tlie  Acropolis,  or 
citadel.  Besides  a  portico  of  six  Doric  columns  on  each  front, 
it  had  an  Ionic  colonnade  within,  and  a  separate  quadrangular 
building  attached  to  each  side.  Before  the  entrance,  are  two 
large  pedestals,  supposed  to  have  supported  equestrian  statues. 
The  Propylaea  were  ascended  by  steps  at  different  stages,  and 
had  also  an  inclined  plane  for  carriages.  This  building  was 
erected  in  the  time  of  Pericles,  and  is  now  in  a  ruinous  state, 
a  great  portion  of  w^hat  remains  being  hidden  by  the  walls  of 
the  Turks.  No.  5,  is  a  transverse  section  of  the  Propylaea, 
made  at  right  angles  with  the  former  veiw,  and  showing  the  dif- 
ferent ascents. 

*  Topography  and  Buildings  of  Athens,  8vo,  1816. 


140 


OF  ARCHITECTURE  AND  BUILDING'. 


No.  6,  is  the  fagade  of  the  Parthenon,  or  temple  of  Miner- 
va, situated  on  the  summit  of  the  Acropolis,  at  Athens.  This 
building  is  now  considered  the  best  model  for  the  Doric  order, 
and  no  edifice,  ancient  or  modern,  commands  such  general  ap- 
plause at  the  present  day.  It  was  built  by  the  architect  Ictinus, 
during  the  administration  of  Pericles,  about  440  years  before 
Christ.  Its  decorative  sculptures  are  supposed  to  have  been 
executed  under  the  direction  of  Phidias.  The  platform  or 
stylobate,  consists  of  three  steps,  the  uppermost  of  which  is 
227  feet  in  length,  and  101  in  breadth.  The  number  of  col- 
umns is  eight  in  the  portico  of  each  front,  and  seventeen  on 
each  flank,  besides  which  there  is  an  inner  row  of  six  columns 
at  each  end  of  the  cell.  The  proportional  height  of  the  col- 
umns is  five  diameters  and  33  minutes,  and  they  diminish  thir- 
teen minutes  in  diameter  from  bottom  to  top.  The  sculptures 
on  the  frieze  represent  the  combats  of  the  Centaurs  and  La- 
pithae.  Those  on  the  eastern  pediment,  represented  the  fabu- 
lous birth  of  Minerva,  and  those  on  the  western,  the  contests 
between  that  goddess  and  Neptune,  for  the  right  of  presiding 
over  the  city.  When  Athens  was  visited  by  Wheler,in  1676, 
the  Parthenon  remained  entire,  with  the  exception  of  its  roof. 
But  during  the  siege  of  the  city  by  the  Venetians,  in  1687,  a 
shell  which  exploded  in  the  midst  of  the  cell,  destroyed  the 
whole  central  part  of  the  wall,  together  with  nineteen  of  the 
columns.  Most  of  the  sculpture  of  both  pediments  has  also 
disappeared. 

No.  7,  is  the  choragic  monument  of  Thrasyllus,  situated 
without  the  Acropolis,  and  constituting  the  front  of  a  grotto.  It 
is  not,  strictly  speaking,  of  any  architectural  order,  but  departs 
from  the  Doric  in  having  a  row  of  circular  wreaths,  instead  of 
triglyphs,  and  a  continuous  row  of  guttae  at  the  bottom  of  the 
frieze. 

No.  8,  is  the  small  Ionic  amphi prostyle  temple  on  the  banks 
of  the  Ilissus,  which  was  standing  in  Stuart's  time,  but  has  now 
wholly  disappeared.  The  delineations  obtained  from  this 
building  by  Stuart,  have  since  furnished  the  most  popular  models 
of  tlie  Ionic  order. 


OP  ARCHITEOTURK   AND  BUILDING. 


141 


No.  9,  is  the  Erectheum,  an  Ionic  building,  much  admired, 
in  the  Acropolis,  at  Athens.  It  comprises  two  temples,  one 
dedicated  to  Minerva  Polias,  the  other  to  the  nymph  Pandro- 
sus.  The  smaller  portico  of  the  Pandroseum,  is  remarkable 
for  a  row  of  Caryatides,  or  female  statues,  which  perform  the 
office  of  columns  in  supporting  the  entablature."'^  No.  10,  is 
an  Ionic  capital  from  the  temple  on  the  Ilissus.  Those  of  the 
temple  of  Minerva  Polias,  were  similar  in  the  general  form  of 
the  volutes,  but  had  also  an  ornamented  neck  above  the 
flutings. 

No.  II.  represents  the  facade  of  the  Temple  of  Apollo 
Didymaeus,  near  Miletus.  It  was  among  the  most  celebrated 
Grecian  structures.  It  was  termed  by  Strabo,  the  greatest  of 
all  temples,  and  was  ranked  by  Vitruvius,  with  that  of  Diana, 
at  Ephesus.  Although  few  of  its  columns  are  now  standing, 
the  ruins  give  evidence  of  its  original  size  and  magnificence. 
It  appears  to  have  been  a  dipteral  temple,  surrounded  with  a 
double  row  of  columns,  triple  in  front,  and  in  all  112.  Views 
of  this  building  are  given  in  the  Ionian  Antiquities,  and  in  the 
Voyage  Pittoresque  of  Choiseul  Gouffier. 

No.  12,  is  the  choragic  monument  of  Lysicrates,  at  Athens, 
sometimes  improperly  called  the  Lantern  of  Demosthenes. 
This  elegant  little  structure  has  a  circular  ornamented  roof  of 
one  stone,  and  six  Corinthian  columns  engaged  in  a  circular 
wall,  the  whole  supported  on  a  square  basis.  It  is  now  half 
inclosed  in  a  modern  convent. 

No.  13,  is  the  Octagon  tower,  at  Athens,  commonly  called 
the  Toiver  of  the  winds,  from  the  emblematic  sculptures  on  its 
sides.  Its  sides  are  marked  with  lines  for  indicating  the  hour 
of  the  day  by  the  shadows  of  gnomons. 

*  One  of  these  statues  Avas  carried  olff  by  Lord  Elgin,  and  is  placed  with 
other  Athenian  marbles  in  the  British  Museum.  Stuart  makes  this  building 
to  consist  of  three  temples,  viz.  those  of  Erectheus,  Minerva  Polias,  and  Pan- 
drosus.    Mr  Wilkins  divides  it  into  two. 


142 


OF  ARCHITECTURE  AND  BUILDING. 


ROMAN  STYLE. 

Roman  architecture  had  its  origin  in  copies  of  the  Greek 
models.  All  the  Grecian  orders  were  introduced  into  Rome, 
and  variously  modified.  Their  number  was  augmented  by  the 
addition  of  two  new  orders,  the  Tuscan  and  the  Composite. 

Tuscan  Order. — This  order,  derived  from  the  ancient  Etrus- 
cans, is  not  unhke  the  Doric  deprived  of  its  triglyphs  and  mutu- 
les.  It  had  a  simple  base  containing  one  torus.  Its  column  was 
seven  diameters  in  height,  with  an  astragal  below  the  capital. 
Its  entablature,  somewhat  Hke  the  Ionic,  consisted  of  plain, 
running  surfaces.  There  is  no  vestige  of  this  order  among  an- 
cient ruins,  and  the  modern  examples  of  it  are  taken  from  the 
descriptions  of  Vitruvius  [PI.  VII.  Fig.  6].  • 

Roman  Doric, — The  Romans  modified  the  Doric  order  by 
increasing  the  height  of  its  column  to  eight  diameters.  Instead 
of  the  echinus  which  formed  the  Grecian  capital,  they  employ- 
ed the  ovolo,  with  an  astragal  and  neck  below  it.  They  placed 
triglyphs  over  the  centre  of  columns,  not  at  the  corners,  and  used 
horizontal  mutules,  or  introduced  foreign  ornaments  in  their  stead. 
The  Theatre  of  Marcellus  has  examples  of  the  Roman  Doric 
[PI.  VII.  Fig.  8]. 

Roman  Ionic. — The  Romans  diminished  the  size  of  the  vo- 
lutes in  the  Ionic  order.  They  also  introduced  a  kind  of  Ionic 
capital  in  w^hich  there  were  four  pairs  of  diagonal  volutes,  in- 
stead of  two  pairs  of  parallel  ones.  This  they  usually  added 
to  parts  of  some  other  capital,  but  at  the  present  day  it  is  often 
used  alone,  under  the  name  of  modern  Ionic. 

Composite  Order. — This  fifth  order  was  made  by  the  Ro- 
mans out  of  the  Corinthian,  simply  by  combining  its  capital  with 
that  of  the  diagonal,  or  modern  Ionic  [PI.  VII.  Fig.  11]. 
Its  best  example  is  found  in  the  arch  of  Titus.  The  favorite 
order,  however,  in  Rome  and  its  colonies,  was  the  Corinthian, 
and  it  is  this  order  which  prevails  among  the  ruins,  not  only  of 
Rome,  but  of  Nismes,  Pola,  Palmyra,  and  Balbec. 


OF  ARCHITECTURE   AND  BITILDTNfi- 


143 


Roman  Structures, — The  temples  of  the  Romans,  sometimes 
resembled  those  of  the  Greeks,  but  often  differed  from  them. 
The  Pantheon,  which  is  the  most  perfectly  preserved  temple 
of  the  Augustan  age,  is  a  circular  building,  hghted  only  from  an 
aperture  in  the  dome,  and  having  a  Corinthian  portico  in  front. 
The  amphitheatre  differed  from  the  theatre,  in  being  a  complete 
circular,  or  rather  elliptical  building,  filled  on  all  sides  with  as- 
cending seats  for  spectators,  and  leaving  only  the  central  space, 
called  the  arena,  for  the  combatants  and  public  shows.  The 
Coliseum  is  a  stupendous  structure  of  this  kind.  The  aque- 
ducts were  stone  canals,  supported  on  massive  arcades,  and 
conveying  large  streams  of  water,  for  the  supply  of  cities.  The 
triumphal  arches,  were  commonly  solid  oblong  structures,  orna- 
mented with  sculptures,  and  open  with  lofty  arches  for  passen- 
gers below  [PI.  VI.  Fig.  8].  The  Basilica  of  the  Romans, 
'  was  a  Hall  of  Justice,  used  also  as  an  exchange,  or  place  of 
meeting  for  merchants.  It  was  lined  on  the  inside  with  colon- 
nades of  two  stories,  or  with  two  tiers  of  columns  one  over  the 
other.  The  earliest  christian  churches  at  Rome,  were  some- 
times called  basilicae,  from  their  possessing  an  internal  colon- 
nade. The  monumental  pillars,  were  towers  in  the  shape  of 
a  column  on  a  pedestal,  bearing  a  statue  on  the  summit,  which 
was  approached  by  a  spiral  staircase  within.  Sometimes,  how- 
ever, the  column  was  solid.  The  Thermce,  or  baths,  were  vast 
structures,  in  which  multitudes  of  people  could  bathe  at  once. 
They  were  supplied  with  warm  and  cold  water,  and  fitted  up 
with  numerous  rooms  for  purposes  of  exercise  and  recreation. 

Remarks. — In  several  particulars,  the  Roman  copies  differed 
from  the  Greek  models  on  which  they  were  founded.  The 
stylobate  or  substructure,  among  the  Greeks,  was  usually  a  plain 
succession  of  platforms,  constituting  an  equal  access  of  steps, 
to  all  sides  of  the  building.  Among  the  Romans,  it  became 
an  elevated  structure,  hke  a  continued  pedestal,  accessible  by 
steps  only  at  one  end.  The  spiral  curve  of  the  Greeks,  was 
exchanged  for  the  geometrical  circular  arc,  as  exemplified  in 
the  substitution  of  the  ovolo  for  the  echinus  in  the  Doric  capital. 


144 


OF  AilCHITECTURE  AND  BUILDING. 


The  changes  in  the  orders,  have  been  already  mentioned. 
After  the  period  of  Hadrian,  Ronian  architecture  is  considered 
to  have  been  on  the  dechne.  Among  the  marks  of  a  deterior- 
ated style  introduced  in  the  later  periods,  v^^ere  columns  with 
pedestals,  columns  supporting  arches,  convex  friezes,  entab- 
latures squared  so  as  to  represent  the  continuation  of  the  col- 
umns, pedestals  for  statues  projecting  from  the  sides  of  col- 
umns, niches  covered  with  little  pediments,  he.  See  Plates 
VI.  and  VII. 

Plate  V. — In  this  plate,  is  represented  a  series  of  buildings 
in  the  Roman  style,  reduced  to  a  scale  after  Durand.  They 
are  all  of  the  Corinthian  order.  No.  1,  is  the  Pantheon,  al- 
ready mentioned,  of  which  the  portico  is  of  stone,  while  the 
body,  or  circular  part  covered  by  the  dome,  is  of  brick.  The 
occurrence  in  this  building,  of  two  pediments,  one  above  the 
other,  is  considered  a  defect,  and  probably  indicates  that  the 
parts  of  the  edifice  were  erected  at  dilFerent  times.  The  en- 
'  tablature  consists  only  of  a  cornice.  In  most  other  respects, 
the  symmetry  of  this  building  is  much  admired. 

No.  2,  is  the  Temple  of  Antoninus  and  Faustina,  at  Rome. 
The  walls  and  columns  are  raised  upon  an  elevated  stylobate 
and  are  approached  by  steps  in  front  only,  differing  in  this  re- 
spect from  the  Grecian  temples,  which  were  accessible  on  all 
sides. 

No.  3,  is  the  Maison  carree  at  Nismes,  in  France.  It  is 
pseudo-peripteral,  having  its  columns  engaged  in  the  wall,  with 
the  exception  of  ten,  which  form  the  portico  in  front.  It  has 
been  lately  discovered  that  this  building,  which  remains  in  ex- 
cellent preservation,  was  erected  to  the  memory  of  Caius  and 
Lucius  Caesar,  sons  of  Agrippa,  and  grandsons  of  Augustus.* 

*  The  origin  and  date  of  this  beautiful  temple  were  unknown,  until  an  ar- 
tist, named  Seguier,  made  out  the  inscription  on  the  frieze,  by  connecting  to- 
gether the  holes  in  which  the  nails  were  driven,  that  formerly  confined  bronze 
letters  upon  the  wall. 


OF   ARCHITECTURE   AND  BUILDING. 


145 


No.  4,  is  the  circular,  peripteral  temple  of  Vesta,  at  Rome. 
The  temple  of  Vesta,  at  Tivoli,  outlined  in  Plate  I,  differs  from 
this,  in  having  a  raised  stylobate.  The  dome,  in  both  these 
buildings,  is  an  imaginary  restoration,  made  after  the  rules  of 
Vitruvius.  Messrs  Taylor  and  Cresy  have  given  to  the  templef 
at  Tivoh,  a  conical  roof  like  that  of  the  monument  of  Lysi- 
crates. 

No.  5,  is  a  temple  at  Pola,  in  Istria,  dedicated  to  Rome  and 
Augustus.  At  this  place  are  many  interesting  antiquities, 
among  which  are  an  amphitheatre  and  triumphal  arch. 

No.  6,  is  the  structure  commonly  called  the  Arch^of  Theseus, 
at  Athens.  It  was  erected  probably  by  the  Roman  emperor  Ha- 
drian, to  divide  the  new  city  from  the  old,  and  bears  an  inscrip- 
tion on  each  side,  indicating  that  on  one  side  is  seen  the  city  of 
Theseus,  and  on  the  other  the  city  of  Hadrian. 

No.  7,  is  a  sepulchre  at  Mylassa,  in  Asia  Minor,  apparently 
of  Roman  origin,  and  described  in  the  Ionian  antiquities.  Its 
angular  pillars  are  square,  but  the  intermediate  columns  have 
a  form  very  unusual  in  ancient  or  modern  architecture,  being 
compressed,  so  that  a  section  of  the  shaft  represents  an  ellipse. 
They  are  fluted  for  half  their  length. 

No.  8,  is  the  triumphal  arch  of  Constantine,  at  Rome,  which, 
with  the  exception  of  a  part  of  its  sculptures,  is  entire  at  the 
present  day.  This  arch  was  built  after  the  arts  had  begun  to 
decline,  and  is  constructed  chiefly  of  materials  taken  from  the 
arch  of  Trajan,  erected  two  centuries  before.  Its  columns 
stand  upon  separate,  projecting  pedestals,  and  have  a  part  of 
the  entablature  squared  upon  the  top  of  each. 

No.  9,  is  the  external  portico  of  the  Temple  of  the  Sun,  at 
Palmyra.  The  ruins  of  this  city  exceed  in  extent  and  magnifi- 
cence anything  else  which  remains  of  antiquity  in  Europe,  or 
Asia.  It  is  built  in  the  Corinthian  order,  and  in  the  later  style 
of  Roman  architecture,  characterized  by  niches  in  the  walls  at 
different  heights  containing  statues,  by  numerous  small  pedi- 
ments and  entablatures,  also  in  some  cases  by  statues  support- 
ed on  brackets,  or  pedestals  projecting  from  the  sides  of  columns. 
19 


146 


OF  ARCHITECTURE   AND  BUILDING. 


In  this  portico,  an  example  occurs  of  double  columns,  a  fea- 
ture rarely  met  with,  in  antique  architecture,  but  sometimes  used 
by  the  moderns,  upon  an  extensive  scale.* 

No.  10,  is  the  circular  temple  at  Balbec,  a  place  distinguish- 
ed by  the  magnificence  and  colossal  size  of  its  ruins.  This 
temple  is  singular  in  the  form  of  its  outline,  which  is  circular, 
with  large  concave  recesses  between  all  the  columns,  as  shown 
more  distinctly  in  the  ground  plan.  No.  11,  of  the  same  build- 
ing.   In  other  respects  it  partakes  of  the  later  Roman  style. 

No.  12,  is  the  octagonal  temple  of  Jupiter,  forming  part  of 
the  palace  erected  by  the  Roman  emperor  Diocletian,  at  Salo- 
na,  now  Spalatro,  in  Dalmatia,  where  its  extensive  ruins  are 
still  extant. 

GRECO-GOTHIC  STYLE. 

After  the  dismemberment  of  the  Roman  empire,  the  arts 
degenerated  so  far,  that  a  custom  became  prevalent  of  erecting 
new  buildings  with  the  fragments  of  old  ones,  which  were  di- 
lapidated and  torn  down  for  the  purpose.  This  gave  rise  to  an 
irregular  style  of  building,  which  continued  to  be  imitated,  es- 
pecially in  Italy,  during  the  dark  ages.  It  consisted  of  Grecian 
and  Roman  details,  combined  under  new  forms,  and  piled  up 
into  structures  wholly  unlike  the  antique  originals.  Hence  the 
names  Greco-gothic  and  Romanesque  architecture  have  been 
given  to  it.  It  frequently  contained  arches  upon  columns,  form- 
ing successive  arcades,  which  were  accumulated  above  each 
other  to  a  great  height.  The  effect  was  sometimes  imposing. 
The  Cathedral  and  Leaning  Tower  at  Pisa,  and  the  Church  of 
St  Mark,  at  Venice,  are  cited  as  the  best  specimens  of  this 
style  [PI.  1.  Fig.  15.  and  PI.  VII.  Fig.  13].  The  Sax- 
on architecture,  used  anciently  in  England,  has  some  things  in 
common  with  this  style  [PI.  VII.  Fig.  14]. 

*  To  the  regular  duplicature  of  columns  inti-oduced  in  the  colonnade  of  the 
Louvre, in  Paris,  Perrault  has  given  the  name  oi arceo-systyle.  See  note  p.  137. 


OF  All€IIITECTUllE   AND  BUILDING. 


147 


SARACENIC  STYLE. 

The  edifices  erected  by  the  Moors  and  Saracens  in  Spain, 
Egypt,  and  Turkey,  are  distinguished,  among  other  things,  by 
a  peculiar  form  of  the  arch.  This  is  a  curve,  constituting  more 
than  half  of  a  circle,  or  ellipse.  This  construction  of  this 
arch,  is  unphilosophical,  and  comparatively  insecure.  A  simi- 
lar peculiarity  exists  in  the  domes  of  the  oriental  Mosques, 
which  are  sometimes  large  segments  of  a  sphere,  appearing  as 
if  inflated ;  and  at  other  times  concavo-convex  in  their  outline, 
as  in  the  mosque  of  Achmet.  The  minaret  is  a  tall  slender 
tower,  peculiar  to  Turkish  architecture.  A  peculiar  flowery 
decoration  called  arabesque,  is  common  in  the  Moorish  build- 
ings of  Europe,  and  Africa  [PI.  VI.  Fig.  3.— PI.  VII. 
Fig.  16,  PI.  I.  Fig.     and  q\. 

GOTHIC  STYLE. 

The  Goths,  who  plundered  Rome,  had  nothing  to  do  with 
the  invention  of  Gothic  architecture.  The  name  was  introduc- 
ed by  Sir  Christopher  Wren,  and  others,  as  a  term  of  reproach, 
to  stigmatize  the  edifices  of  the  middle  ages,  which  departed 
from  the  purity  of  the  antique  models.  The  term  was,  at  first, 
very  extensive  in  its  application,  but  it  is  now  confined  chiefly, 
to  what  may  be  called  the  modern  Gothic, — the  style  of  build- 
ing cathedrals,  churches,  abbeys,  Sic.  which  was  introduced  in 
England  six  or  eight  centuries  ago,  and  adopted,  nearly  at  the 
same  time,  in  France,  Germany,  and  other  parts  of  Europe. 
The  Gothic  style  is  peculiar  and  strongly  marked.  Its  princi- 
ple seems  to  have  originated  in  the  imitation  of  groves,  and 
bowers,  under  which  the  Druids  performed  their  sacred  rites. 
Its  characteristics,  at  sight,  are,  its  pointed  arches,  its  pinnacles 
and  spires,  its  large  buttresses,  clustered  pillars,  vaulted  roofs, 
profusion  of  ornaments,  and  the  general  predominance  of  the 
perpendicular  over  the  horizontal. 


148 


OF  ARCHITECTURE  AND  BUILDING. 


Definitions. — As  the  common  place  for  the  display  of  Goth- 
ic architecture,  has  been  in  ecclesiastical  edifices,  it  is  necessa- 
ry to  understand  the  usual  plan  and  construction  of  these  build- 
ings. A  church  or  cathedral  is  commonly  built  in  the  form  of 
a  cross,  having  a  tower,  lantern,  or  spire,  erected  at  the  place 
of  intersection.  The  part  of  the  cross,  situated  toward  the 
west,  is  called  the  nave.  The  opposite  or  eastern  part  is  called 
the  choir,  and  within  this  is  the  chancel.  The  ti*ansverse  por- 
tion, forming  the  arms  of  the  cross,  is  called  the* transept. 


Nave 


Choir 


Any  high  building  erected  above  the  roof,  is  called  a  steeple; 
if  square  topped,  it  is  a  tower;  if  long  and  acute  a  spire,  and 
if  short  and  light,  a  lantern.  Towers  of  great  height,  in  pro- 
portion to  their  diameter,  are  called  turrets.  The  walls  of 
Gothic  churches,  are  supported  on  the  outside,  by  lateral  pro- 
jections, extending  from  top  to  bottom,  at  the  corners,  and  be- 
tween the  windows.  These  are  called  buttresses,  and  they  are 
rendered  necessary  to  prevent  the  walls  from  spreading  under 
the  enormous  weight  of  the  roofs  [PI.  VI.  Fig.  4,  and  5]. 
On  the  tops  of  the  buttresses,  and  elsewhere,  are  slender  pyra- 
midal structures,  or  spires,  called  pinnacles.  These  are  orna- 
mented on  their  sides,  with  rows  of  projections,  appearing  like 
leaves  or  buds,  which  are  named  crockets.  The  summit,  or 
upper  edge  of  a  wall,  if  straight,  is  called  a  parapet ;  if  indent- 
ed, a  battlement.  Gothic  windows  were  commonly  crowned 
with  an  acute  arch.  They  were  long  and  narrow,  or  if  wide, 
were  divided  into  perpendicular  lights  by  mullions.    The  lateral 


OF  ARCHITECTURE  AND  BUILDING. 


149 


spaces  on  the  upper  and  outer  side  of  the  arch,  are  called 
spandrells ;  and  the  ornaments  in  the  top,  collectively  taken, 
are  the  tracery.  An  oriel,  or  bay  window,  is  a  projecting  win- 
dow. A  wheel,  or  rose  window,  is  large  and  circular.  A  cor- 
bel, is  a  bracket  or  short  projection  from  a  wall,  serving  to  sus- 
tain a  statue,  or  the  springing  of  an  arch. 

Gothic  pillars  or  columns,  are  usually  clustered,  appearing 
as  if  a  number  were  bound  together.  The  single  shafts  thus 
connected,  are  called  boltels.  They  are  confined  chiefly  to  the 
inside  of  buildings,  and  never  support  anything  like  an  entab- 
lature. Their  use  is  to  aid  in  sustaining  the  vaults  under  the 
roof,  which  rest  upon  them  at  springing  points  [PI.  VI.  Fig. 
6].  Gothic  vaults  intersect  each  other,  forming  angles  called 
groins.  The  parts  which  are  thrown  out  of  the  perpendicular 
to  assist  in  forming  them,  are  the  pendentives.  The  ornament- 
ed edge  of  the  groined  vault,  extending  diagonally,  like  an 
arch,  from  one  support  to  another,  is  called  the  ogyve.  The 
gothic  term  gable,  indicates  the  erect  end  of  a  roof,  and  an- 
swers to  the  Grecian  pediment,  but  is  more  acute. 

The  Gothic  style  of  building  is  more  imposing,  and  more 
difficult  to  execute,  than  the  Grecian.  This  is  because  the 
weight  of  its  vaults  and  roofs  is  upheld  at  a  great  height,  by 
supporters  acting  at  single  points,  and  apparently  but  barely 
sufficient  to  effect  their  object.  Great  mechanical  skill  is  ne- 
cessary, in  balancing  and  sustaining  the  pressures,  and  archi- 
tects at  the  present  day,  find  it  difficult  to  accomplish  what  was 
achieved  by  the  builders  of  the  middle  ages. 

Plate  VI. — No.  1,  is  the  front  of  an  ancient  Egyptian  tem- 
ple, at  Essenay.  It  has  the  sloping  walls,  concave  entablature, 
crowded  columns,  and  hieroglyphic  sculptures,  peculiar  to  the 
edifices  of  that  country.  The  roof  is  flat,  and  supported  on 
twentyfour  columns  inside. — No.  2,  represents  an  octagonal 
pagoda,  at  Sinkicien,  in  China.  It  gives  an  example  of  the 
curved  Chinese  roof,  formed  in  imitation  of  the  tent. — No.  3, 
is  the  Mosque  of  Achmet,  at  Constantinople,  built  in  1610. 


150 


OF  ARCHITECTURE  AND  BUILDING. 


It  has  a  central  dome,  surrounded  by  four  half  domes,  which 
cover  vast  recesses  resembling  niches.  Its  court  is  surrounded 
by  a  sort  of  cloister,  covered  by  numerous  small  cupolas,  and 
having  tall  minarets  at  the  angles  and  sides. — No.  4,  is  a  per- 
spective view  of  York  Cathedral,  one  of  the  most  admired 
specimens  of  Gothic  architecture.  It  is  built  in  the  form  of  a 
cross,  and  has  three  towers,  of  which  the  two  front  ones  are 
surmounted  by  pinnacles,  and  the  central  one  by  battlements. 
It  was  built  between  the  years  1171  and  1426. — No.  5,  is  a 
Gothic  exterior,  from  the  wall  of  Westminster  Abbey,  showing 
the  buttresses,  which  support  the  walls,  also  the  short  pinnacles 
and  battlements.  The  slanting  braces  at  top  are  called  flying 
buttresses. — No.  6,  is  a  Gothic  interior,  from  the  nave  of  York 
Cathedral.  It  shows  the  clustered  pillars,  pointed  arches,  groin- 
ed vaulting,  and  tracery,  which  belong  to  the  Gothic  style. 

Plate  VII. — In  this  plate  is  presented  a  series  of  columns 
with  some  of  their  entablatures,  arches,  &ic.,  illustrative  of  the 
styles  of  building  which  have  prevailed  in  different  epochs,  and 
countries.  The  three  first  figures  are  those  of  Egyptian  col- 
umns, all  serving  to  show  the  massiveness  of  structure  which 
prevailed  in  the  buildings  of  that  nation.  A  great  variety  of 
these  columns  exist  at  the  present  day  in  Upper  Egypt,  partic- 
ularly at  Karnac  and  Luxor,  the  remains  of  ancient  Thebes. 
No.  1,  is  from  a  tomb  of  Silsilis,  and  has  an  outline  which  is 
common  among  the  Egyptian  ruins. — No.  2,  likewise  a  com- 
mon form,  has  a  capital  composed  of  faces. — No.  3,  is  a  column 
from  Komonbu.  The  idea  of  the  Corinthian  capital,  seems 
to  have  been  borrowed  from  Egyptian  specimens  of  this  kind. 
The  column  No.  4,  is  from  the  great  cave  at  Elephanta,  near 
Bombay,  one  of  the  wonderful  subterranean  structures  exca- 
vated by  the  ancient  inhabitants  of  Hindostan  out  of  solid  rock. 
No.  5,  is  a  column  from  the  ruins  of  Persepolis.  At  this  place, 
which  contains  the  most  remarkable  relics  of  the  ancient  arts 
of  Persia,  the  style  of  architecture  partakes  of  the  Egyptian 
and  Hindoo  characteristics,  the  columns,  however,  being  more 
slender. — No.  6,  represents  the  Tuscan  order,  used  by  the  an- 


OF  ARCHITECTURE   AND  BUILDING. 


151 


cient  inhabitants  of  Etruria. — No.  7,  is  the  Grecian  Doric,  of 
the  age  of  Pericles,  at  which  time  it  is  considered  to  have  been 
in  greatest  perfection. — No.  8,  is  the  Roman  Doric,  represent- 
ed with  a  base,  after  the  restorations  of  the  moderns. — No.  9, 
is  the  Grecian  Ionic.  The  base  represented  in  this  figure,  and 
the  next,  is  called  the  Attic  base. — No.  10,  the  Corinthian  or- 
der.— No.  11,  the  Composite  Order,  in  which  the  volutes  are 
larger  than  in  the  Corinthian.  The  modern  Ionic  is  taken 
from  the  upper  part  of  this  capital.  The  frieze  is  represented 
as  convex,  a  feature  which  is  considered  peculiar  to  the  later 
or  declining  period  of  Roman  architecture. — No.  12,  is  a  com- 
bination of  the  column  with  a  pedestal,  and  a  squared  portion 
of  the  entablature,  usually  attached  to  the  main  edifice,  by 
one  side.  This  peculiarity  was  introduced  after  the  arts  had 
begun  to  decline,  and  appears  in  many  of  the  later  Roman  edi- 
fices. It  has  been  absurdly  imitated  in  more  modern  times,  by 
making  a  squared  entablature  to  constitute  a  portion  of  the  col- 
umn, and  placing  another  entablature  above  it. — No.  13,  shows 
a  mode  of  building  with  arches  between  the  columns  and  the 
entablature.  It  is  taken  from  the  remains  of  Diocletian's  pal- 
ace at  Spalatro,  and  seems  to  have  given  rise  to  the  Greco- 
gothic  style. — No.  14,  which  also  exhibits  arches  upon  columns, 
is  a  specimen  of  Saxon  architecture  from  the  Cathedral  at  Ely. 
No.  15,  is  a  twisted  column  from  a  cloister  belonging  to  St 
Paul's  church,  without  the  walls,  at  Rome,  rebuilt  about  the 
year  800.  Columns  of  this  sort  occur  in  various  Italian  struc- 
tures, but  it  is  difficult  to  conceive  of  a  form  more  at  variance 
with  architectural  fitness  or  security. — No.  16,  Moorish  double 
columns,  arches,  and  arabesques,  from  the  Alhambra,  at  Gren- 
ada. In  the  same  building,  the  true  Saracenic  or  horse-shoe 
arch,  also  occurs. — No.  17,  a  Gothic  pillar  from  Salisbury 
Cathedral.  Other  Gothic  forms  are  seen  in  Plate  VI.  Fig.  6. 
No.  18,  a  Chinese  column  from  the  viceroy's  palace,  at  Canton. 
No.  19,  section  of  a  reeded  Egyptian  column. — No.  20,  sec- 
tion of  a  fluted  Doric  column. — No.  21,  section  of  a  fluted 


152  OF   ARCHITECTURE   AND  BUILDING. 

Ionic  column. — No's  22,  23,  and  24,  sections  of  different 
Gothic  columns. 

Application. — In  edifices  erected  at  the  present  day,  the 
Grecian  and  Gothic  outlines,  are  commonly  employed  to  the 
exclusion  of  the  rest.  In  choosing  between  them,  the  fancy  of 
the  builder,  more  than  any  positive  rule  of  fitness,  must  direct 
the  decision.  Modern  dwelling  houses  have  necessarily  a  style 
of  their  own,  as  far  as  stories  and  apartments,  and  windows  and 
chimnies,  can  give  them  one.  No  more  of  the  styles  of  former 
ages  can  be  applied  to  them,  than  what  may  be  called  the  un- 
essential and  decorative  parts.  In  general,  the  Grecian  style, 
from  its  right  angles  and  straight  entablatures,  is  more  conveni- 
ent and  fits  better  with  the  distribution  of  our  common  edifices, 
than  the  pointed  and  irregular  Gothic.  The  expense  also  is 
generally  less,  especially  if  anything  like  thorough  and  genuine 
Gothic  is  attempted;  a  thing,  however,  rarely  undertaken  as 
yet,  in  this  country.  But  the  occasional  introduction  of  the 
Gothic  outline,  and  the  partial  employment  of  its  ornaments, 
has  undoubtedly  an  agreeable  effect,  both  in  public  and  private 
edifices;  and  we  are  indebted  to  it,  among  other  things,  for  the 
spire,  a  structure  exclusively  Gothic,  which,  though  often  mis- 
placed, has  become  an  object  of  general  approbation,  and  a 
pleasing  landmark  to  our  cities  and  villages. 


WiLKiNs'  Translation  of  Vitruvius,  4to.  1817; — ^Elmes'  Lectures 
on  Architecture,  8vo.  1823 ; — Stuart's  Antiquities  of  Athens,  4  vols, 
fol.  1762,  &c. ; — Antiquities  of  Ionia,  by  the  Dilettanti  Society,  2 
vols,  fol.  1817-21 ; — Antiquities  of  Attica,  by  the  same,  fol.  1817 ; — 
Wilkin  s' Magna  Grsecia,  fol.  1807; — Desgodetz's  Buildings  of  Rome, 
2  vols,  fol.  tra.  1771 ; — Taylor  and  Cresys'  Antiquities  of  Rome,  2  vols, 
fol.  1821-2; — DuRAND,i2ecMet7c?e5  Edifices,  ohlongM.  1801; — Pugins' 
Specimens  of  Gothic  Architecture,  2  vols,  4to.  1823; — Brittons* 
Architectural  Antiquities  of  Great  Britain,  4  vols,  4to.  1815,  &c. ; — 
Tredgold's  Elements  of  Carpentry,  4to.  1821; — Nicholsons' Archi- 
tectural Dictionary,  3  vols,  4to.  1821. 


CHAPTER  VIII. 


ARTS  OF  HEATING  AND  VENTILATION. 

In  cold  and  temperate  climates,  a  large  portion  of  human 
labor  is  devoted  to  procure  and  sustain  such  a  degree  of  heat, 
as  is  necessary  to  a  comfortable  existence.  The  means  of  ef- 
fecting this  object,  as  far  as  the  economy  of  fires  and  dwelling 
houses  is  concerned,  will  be  considered  in  the  present  chapter. 
To  procure  heat,  to  distribute  it,  to  retain  it,  and  to  obviate  its 
inconvienences  by  ventilation,  are  the  principal  objects  that 
present  themselves  in  a  survey  of  the  subject. 

PRODUCTION  OF  HEAT. 

Fuel. — Heat  is  artificially  obtained  for  common  purposes,  by 
the  combustion  of  fuel.  Fuel  may  be  usefully  considered  with 
regard  to  its  compactness  or  weight,  its  quantity  of  combustible 
matter,  and  its  quantity  of  water. 

Weight  of  Fuel. — In  regard  to  the  first  consideration,  if 
other  things  be  equal,  the  more  compact  and  heavy  any  fuel  is, 
the  more  difficult  it  is  to  kindle,  but  the  more  permanent  will  it 
be  found  when  once  on  fire.  Coal,  for  example,  is  a  compact 
fuel,  when  compared  with  light  dry  wood.  Coal  cannot  so  well 
be  kindled  by  a  small  blaze,  nor  by  a  very  small  quantity  of  oth- 
er combustible  matter  on  fire,  because  its  density  renders  it  a 
rapid  conductor,  and  it  carries  off  the  heat  of  the  kindling  sub- 
stance, so  as  to  extinguish  it,  before  it  is  itself  raised  to  the 
temperature  necessary  for  its  combustion.  But  if  the  heat  of  oth- 
er fuel  be  applied  to  it  in  sufficient  quantity,  and  long  enough, 
to  ignite  it,  it  then  produces  a  powerful  fire,  and  a  much  more 
durable  one  than  lighter  fuel.  Light  fuel,  on  the  other  hand, 
20 


154 


ARTS  OF  HEATING  AND  VENTILATION, 


being  a  slow  conductor  of  heat,  kindles  easily ;  and,  from  the 
admixture  of  atmospheric  air  in  its  pores  and  crevices,  burns 
out  rapidly,  producing  a  comparatively  temporary,  though  often 
a  strong,  heat. 

Combustible  matter  oj  Fuel. — The  quantity  of  combustible 
matter  of  fuel,  if  the  weight  and  other  circumstances  be  equal, 
may  be  learnt  from  the  ashes,  or  residuum,  left  after  the  com- 
bustion. For  example,  good  Newcastle  coal,  contains  a  great- 
er portion  of  combustible  matter,  than  Nova  Scotia  coal,  and 
leaves  behind  a  smaller  amount  of  earthy  and  incombustible 
substance.  The  heating  pow  er,  and  consequent  value,  of  dif- 
ferent kinds  of  fuel,  is  affected  by  this  circumstance,  though  by 
no  means  dependent  on  it.  The  fitness  of  fuel  for  various  pur- 
poses, is  furthermore  affected  by  the  facility,  w  ith  which  it  gives 
off  a  part  of  its  combustible  matter  in  the  form  of  vapor,  or 
gas  ;  which,  being  burnt  in  that  state,  ^troduces  flame.  *  For  ex- 
ample, the  bituminous  coals  abound  in  volatile  matter,  which, 
when  ignited,  supports  a  powerful  blaze.  On  the  other  hand, 
the  Lehigh  and  Rhode  Island  coals  are  destitute  of  bitumen, 
and  yield  but  little  flame.  It  is  from  similar  causes,  that  dry 
pine  wood  produces  a  powerful  blaze,  while  its  charcoal  yields 
comparatively  httle.  A  blaze  is  of  great  service,  where  heat  is 
required  to  be  applied  to  an  extensive  surface,  as  in  reverberat- 
ing furnaces,  ovens,  glass  houses,  he.  But  when  an  equable, 
condensed,  or  lasting  fire  is  wanted,  the  more  solid  fuels,  which 
blaze  less,  are  to  be  preferred. 

Water  in  Fuel. — The  quantity  of  watery  fluid  contained  in 
fuel,  greatly  affects  the  amount  of  heat  it  produces,  much  more 
indeed,  than  is  commonly  admitted  in  practice.  It  is  a  well 
known  law  of  chemistry,  that  the  evaporation  of  liquids,  or 
their  conversion  into  steam,  consumes,  and  renders  latent,  a 
great  amount  of  caloric.  When  green  wood,  or  wet  coal,  are 
added  to  the  fire,  they  abstract  from  it  by  degrees,  a  sufficient 
part  of  its  heat,  to  convert  their  own  sap  or  moisture  into  steam, 
before  they  are  capable  of  being  burnt.    And  as  long  as  any 

*  See  Chapter  IX.  Art.  Flame. 


ARTS  OF  HEATING  AND  VENTILATION. 


155 


considerable  part  of  this  fluid  remains  unevaporated,  the  com- 
bustion goes  on  slowly,  the  fire  is  dull,  and  the  heat  feeble. 
Green  wood  commonly  contains  a  third,  or  more,  of  its  weight 
of  watery  fluid,  the  quantity  varying  according  to  the  greater 
or  less  porosity  of  different  trees.  Nothing  is  further  from  true 
economy  than  to  burn  green  wood,  or  wet  coal,  on  the  suppo- 
sition that  because  they  are  more  durable,  they  will  in  the  end 
prove  more  cheap.  It  is  true,  their  consumption  is  less  rapid  ; 
but  to  produce  a  given  amount  of  heat,  a  far  greater  amount  of 
fuel  must  be  consumed.  Wood  that  is  dried  under  cover  is  bet- 
ter than  wood  dried  in  the  open  air,  being  more  free  from  de- 
composition. 

Not  only  the  production  of  steam,  but  likewise  the  formation 
of  different  gases,  which  are  evolved  during  combustion,  af- 
fect the  usefulness  of  fuel,  according  to  their  quantity  and  ca- 
pacity for  heat.  It  is  difficult,  however,  to  estimate  with  accu- 
racy the  amount  of  their  practical  effect. 

Charcoal, — Charcoal  is  prepared  from  wood,  and  coke  in  a 
similar  manner  from  pitcoal ;  by  raising  those  substances  to  a 
high  temperature,  sufficient  to  deprive  them  of  their  moisture 
and  volatile  matter.  When  intended  for  chemical  uses,  char- 
coal is  made  by  exposing  wood  to  heat  in  iron  cylinders,  or 
other  close  vessels.  But  for  the  common  purposes  of  fuel,  it 
is  made  by  a  sort  of  smothered  combustion,  in  which  masses  of 
wood,  when  set  on  fire,  are  covered  with  earth,  so  as  nearly  to 
exclude  the  atmospheric  air.  This  exclusion  of  air  prevents 
the  wood  from  being  consumed,  while  the  red  heat,  which  is 
kept  up  for  some  time,  dissipates  the  moisture  from  its  pores. 
Charcoal  is  generated  in  a  small  way,  every  night,  in  fires 
which  are  raked  up ;  the  brands  and  half  burnt  coals,  are  kept 
from  consuming,  by  the  partial  exclusion  of  the  air,  while  the 
light  ashes,  being  a  slow  conductor  of  caloric,  prevent  them  from 
cooling  below  a  red  heat.  Charcoal,  when  newly  made  from 
the  heavier  kinds  of  wood,  such  as  oak  and  walnut,  is  a  power- 
ful, and  for  some  purposes,  an  economical  kind  of  fuel.  Coke, 
a  kind  of  fuel  used  for  certain  purposes  in  England,  is  charred 
pitcoal.    It  produces  a  strong  and  steady  heat,  but  does  not 


156 


ARTS  OF  HEATING  AND  VENTILATION. 


blaze.  Large  quantities  of  coke  are  formed  in  the  manufacto- 
ries of  coal  gas. 

COMMUNICATION  OF  HEAT. 

Radiated  and  conducted  Heat. — Caloric,  or  heat,  is  com- 
municated to  apartments,  by  fires  kept  in  them,  in  two  ways. 
A  part  of  it  is  radiated,  the  rest  is  conducted.  The  first  por- 
tion passes  through  the  air  with  great  velocity,  in  diverging  rays. 
The  second,  penetrates  slowly  through  the  densest  bodies, 
whether  transparent,  or  opaque.  In  a  fire  place  or  open  stove, 
the  heat  which  is  felt  by  holding  the  hand  before  the  fire,  is 
radiated  caloric.  That  which  is  felt  by  placing  the  hand  on 
the  iron  or  bricks,  is  conducted  caloric.  To  enjoy  the  full  ef- 
fect of  radiated  caloric,  we  must  be  in  presence,  or  sight  of 
the  radiating  object.  To  receive  conducted  heat,  we  must  be 
in  contact  with  the  substance  which  imparts  it.  Since,  however, 
we  cannot  remain  in  contact  with  the  fire  itself,  we  derive  our 
conducted  heat  from  the  air,  a  fluid,  which  constandy  touches, 
and  envelopes  our  persons ;  and  which,  when  heated  in  itself, 
becomes  a  source  of  warmth  to  us.  The  object  of  the  various 
contrivances,  known  under  the  names  of  stoves  and  fire  places, 
is  to  enable  us  to  use  fire  with  safety,  and  to  obtain  from  it  a 
due  supply  of  radiated  caloric,  and  heated  air. 

In  common  cases,  radiant  heat  is  more  agreeable,  than  con- 
ducted heat,  when  we  wish  to  obtain  a  sudden  warmth  ;  since 
its  degree  may  be  increased  at  pleasure,  by  altering  our  proxi- 
mity to  the  fire  ;  the  effect  of  the  radiation  being  inversely  pro- 
portionate to  the  square  of  the  distance.  But  as  only  one  half 
of  the  recipient  body  can  be  warmed  at  a  time  by  radiation,  no 
person  surrounded  by  a  cold  atmosphere,  can  be  made  uniform- 
ly warm,  by  the  radiated  heat  of  a  fire.  It  is  only  when  the 
surrounding  atmospheric  air  has  become  warm,  that  we  obtain 
all  the  advantage  which  fire  is  capable  of  affording. 

Fire  in  the  open  Air. — The  simplest,  and  least  effectual 
mode,  by  which  heat  can  be  obtained,  is  from  a  fire  in  the  opejn 


ARTS  OF   HEATING   AND  VENTILATION. 


157 


air.  The  hunter,  or  backwoodsman,  when  he  encamps  for  the 
night,  builds  a  fire  of  logs,  and  lays  down  to  sleep,  with  his  feet 
extended  towards  it.  In  this  situation  he  can  enjoy  only  a  small 
portion  of  the  radiated  heat  of  the  fire,  this  heat  being  thrown 
off  equally  in  all  other  directions.  Of  the  conducted  heat 
he  obtains  none ;  for  the  air  which  surrounds  the  fire 
having  'nothing  to  confine  it,  ascends  by  its  diminished  spe- 
cific gravity,  as  fast  as  it  is  warmed,  and  its  place  is  immediately 
supplied  by  strata  of  colder  air  from  beneath.  Hence  a  cur- 
rent of  cold  air  will  take  place  from  the  atmosphere  on  all 
sides,  towards  the  fire,  so  that  the  person  who  derives  warmth 
from  the  fire  on  one  side,  will  on  the  other  be  exposed  to  addi- 
tional cold.  The  first  step  towards  remedying  this  inconve- 
nience, is  to  build  up  a  barrier,  or  imperfect  wall,  on  the  out- 
side of  the  place  occupied  by  the  tenant.  This  will  intercept 
the  current  of  cold  air,  and  oblige  it  to  approach  the  fire  by  oth- 
er directions,  at  the  same  time  that  it  will  gradually  become  heat- 
ed itself,  and  radiate  back  a  portion  of  its  warmth.  The  next 
improvement  consists  in  extending  the  wall,  so  as  completely 
to  surround  the  fire,  thus  obliging  the  air  to  approach  it  from 
above,  or  from  doors  and  avenues  purposely  left  for  its  entrance. 
This  is,  in  fact,  the  commencement  of  a  dwelling  house.  A 
roof  with  an  aperture  for  the  escape  of  the  smoke,  is  a  further 
improvement  on  the  plan,  and  lastly  the  introduction  of  a  chim- 
ney, at  once  renders  the  mansion  convenient  and  tenantable.  * 
Fire  places. — Chimnies  from  their  usual  situation  in  regard 
to  rooms,  and  also  for  the  sake  of  a  more  perfect  draught,  have 
an  opening  on  one  side  of  their  base,  to  which  we  give  the  name 
of  fire  place.  The  fire  place  in  former  times  was  an  oblong 
or  cubical  cavity,  having  its  sides  nearly  at  right  angles  with 
the  back.  In  a  cavity  of  this  description,  the  greater  part  of 
the  heat  generated  by  the  fire,  was  totally  lost  to  the  apartment, 
nearly  all  the  conducted  heat  being  carried,  with  the  air,  up  the 
chimney ;  while  of  the  radiated  heat,  but  a  small  part  could 
directly  enter  the  room,  viz.  the  part  radiated  from  the  front  of 


*  See  Sylvester's  account  of  the  Derbyshire  Infirmary. 


158 


ARTS  OF   HEATING  AND  VENTILATION. 


the  fire  ;  the  heat  of  the  other  sides  being  chiefly  thrown  into 
the  hearth,  back,  and  sides,  or  up  the  chimney.  In  the  old  fire 
places,  the  inconvenience  was  still  further  augmented  by  in- 
creasing their  dimensions  to  an  enormous  size,  so  that  seats  or 
benches  could  be  placed  on  each  side,  on  the  inside  of  the 
jambs.  The  consequence  was,  that  a  prodigious  current  of  air 
was  constantly  carried  up  the  chimney,  and  the  seats,  on  the 
inside  of  the  fire  place,  became  the  only  comfortable  ones  in 
the  room. 

Admission  of  cold  Air. — It  is  obvious,  that  in  apartments 
with  open  fire  places,  the  air  must  be  continually  shifting,  and 
that  cold  air  must  enter  at  the  crevices  of  the  doors  and  win- 
dows, to  supply  the  place  of  that  which  maintains  the  combus- 
tion, or  escapes  up  the  chimney.  In  moderate  weather  this 
change  of  air  is  an  advantage,  since  it  freshens  and  ventilates 
the  room,  the  air  of  which  would  otherwise  become  close  and 
impure.  In  moderate  weather  also,  the  radiant  heat  is  adequate 
to  warm  the  walls  of  the  room,  which  in  their  turn  become 
sources  of  radiant  heat,  and  likewise  contribute  to  warm  the 
air  by  their  contact.  But  in  very  cold  weather,  it  is  nearly  or 
quite  impossible  to  render  a  large  apartment  warm  by  means  of 
a  common  open  fire  place,  for,  in  proportion  to  the  briskness  of 
the  fire  itself,  will  be  the  rapidity  with  which  the  cold  air  press- 
es into  the  room,  and  a  person  near  the  hearth  feels  perhaps  as 
much  cold  on  one  side  of  his  body,  as  heat  on  the  other. 

Open  Fires. — The  cheerful  sight  of  an  open  fire,  to  which 
habit  and  association  have  attached  us,  has  created  a  strong  and 
almost  general  preference  to  the  open  fire  place  over  the  close 
stove,  and  a  desire,  by  remedying  its  defects,  to  make  it  more 
effectual  and  useful.  Of  various  philosophers  who  have  exer- 
cised their  ingenuity  on  this  subject,  the  two  who  appear  to 
have  labored  with  most  success,  are  our  countrymen,  Dr  Frank- 
lin, and  Count  Rumford. 

FranJdin  Stove. — Dr  Franklin,  whose  writings  on  the  econ- 
omy of  fire  contain  the  basis  of  many  of  the  improvements 
which  have  since  been  introduced,  invented  an  apparatus  of 


ARTS   OP  HEATING  AND  VENTfLATION. 


159 


cast  iron,  to  which  he  gave  the  name  of  the  Pennsylvania  Fire 
place,  but  which  is  now  often  known  by  the  name  of  Franklin 
Stove.  This  fire  place,  when  executed  agreeably  to  the  au- 
thor's instructions,  is  one  of  the  most  effective  and  economical 
modes  in  which  an  open  fire  can  be  managed.  By  means  of 
a  narrow  and  circuitous  smoke  flue,  which  is  surrounded  and 
intersected  with  air  passages,  a  great  part  of  the  heat  of  the 
fire  is  retained  in  the  room,  and  at  the  same  time  a  current  of 
fresh  air,  warmed  by  the  fire  place,  is  introduced  into  the 
apartment.  In  Plate  VIII.  Fig.  1 .  is  seen  a  section  of  the 
Pennsylvania  fire  place.  A,  is  the  place  of  the  fuel  and  fire, 
BCD,  the  smoke  flue,  passing  first  upward,  then  downward 
to^the  floor,  and  escaping  by  the  chimney  D,  next  the  wall,  K. 
E  H,  is  the  air  chamber  into  which  the  air  is  admitted  from 
without  the  house  through  the  passage  I.  After  being  heated, 
it  is  discharged  into  the  apartment  by  lateral  openings  at  the 
top  G.  ^ 

Fire  places  which  stand  out  into  the  room,  also  fire  places 
with  hollow  backs  or  pipes  for  hot  air,  are  to  be  viewed  in  most 
instances,  as  simpHfications  only,  of  Franklin's  plan. 

Rumford  Fire  Place. — Count  Rumford's  fire  place  forms  a 
pleasant  and  effectual  mode  of  enconomizing  the  heat  of  an  open 
fire,  besides  which,  its  cheapness  and  simplicity  give  it  the  ad- 
vantage over  more  complicated  plans,  and  have  occasioned  its 
very  general  introduction.  The  peculiarities  of  this  fire  place 
consist,  1st,  in  an  advanced  back,  which  brings  the  fire  nearer 
into  the  room,  and  at  the  same  time  by  narrowing  the  throat  of 
the  chimney  diminishes  the  current  of  air  which  escapes  through 
it;  2dly,  in  the  oblique  sides  or  covings  of  the  fire  place, 

*  Most  of  the  articles  now  sold  as  Franklin  Stoves,  are  very  different  from 
the  original  Pennsylvania  fire  place.  If  any  defect  existed  in  the  plan  of  the 
inventor,  it  was  in  the  small  quantity  of  air  admitted  through  a  circuitous  and 
obstructed  channel,  and  in  the  bad  character  of  the  material,  cast  iron  being  lia- 
ble to  warp  and  crack  if  exposed  to  great  heat  and  cold  on  opposite  sides. 

The  first  person  who  suggested  the  introduction  of  heated  air,  through 
hollow  passages,  appears  to  have  been  M.  Ganger,  in  a  work  entitled  La 
Mechanique  de  Feu,  published  in  1709, 


160 


ARTS   OF   HEATING   AND  VENTILATION. 


which  are  enabled,  when  heated,  to  radiate  their  warmth  into 
the  room.  Count  Rumford  recommends  that  the  angle,  made  by 
the  sides  with  the  back,  should  be  one  of  135  degrees.  He 
also  advises  that  the  color  of  the  covings  should  be  white, 
this  color  being  best  adapted  for  radiation. 

Double  Fire  Place. — For  parlours,  and  common  apartments, 
no  contrivance  appears  so  pleasant  and  effectual,  as  the  double 
fire  place,  which  has  of  late  years  been  extensively  introduced 
in  this  city  and  vicinity.  It  is  a  modification  of  Franklin's 
plan,  and  is  made  from  any  common  fire  place,  by  inserting 
within  it  another  fire  place  made  of  soapstone,  leaving  an  empty 
space,  of  about  an  inch  in  depth,  between  the  two,  so  that  when 
finished,  the  back  and  sides  maybe  hollow.  This  hollow  space 
does  not  communicate  with  the  fire,  but  has  two  openings,  one 
at  bottom,  communicating  with  the  external  atmosphere  by  a 
perforation  in  the  wall,  or  by  a  tin  pipe  laid  in  the  floor ;  the 
other  opening  into  the  apartment,  at  a  point  higher  than  the  fire 
place,  and  commonly  at  the  side  of  the  chimney.  In  this  fire 
place,  an  open  fire,  of  wood  or  coal,  may  be  used  with  the  full 
advantage,  ever  obtained,  of  its  radiant  heat.  A  large  part  of 
the  conducted  heat  is  also  saved,  since  the  air  which  enters 
from  without,  becomes  heated  in  the  hollow  space,  and  ascends 
by  it  in  consequence  of  its  diminished  specific  gravity,  entering 
the  room  in  a  strong  warm  current.  This  air  serves  the  pur- 
pose of  ventilation,  it  supersedes  the  entrance  of  cold  air  through 
the  crevices  and  key  holes,  and  is  also  a  preventive  against 
smoking.  The  circumstances  to  be  attended  to  in  the  construc- 
tion, are  as  follows.  1.  The  openings  for  the  air  should  be 
large,  in  common  cases  from  four  to  seven  inches  in  diameter, 
since  it  is  better  to  introduce  a  large  quantity  of  air  moderately 
warmed,  than  a  small  quantity  made  very  hot.  More  heat  will 
in  this  case  be  conducted  from  the  stone,  and  the  unpleasant 
effects  of  burnt  air  will  be  avoided.  2.  The  openings  into 
the  room  should  be  made,  when  practicable,  at  least  a  foot  high- 
er than  the  top  of  the  fire  place,  for  when  they  are  on  a  level 
with  it,  or  lower,  the  warm  air  is  liable  to  be  drawn  up  the 


ARTS   OF   HEATING   AND  VENTILATION. 


161 


chimney,  and  the  main  object  defeated.  But  if  the  opening  is 
above  the  fire  place,  then  the  warm  air  will  ascend  and  be  dif- 
fused through  the  upper  parts  of  the  room,  till  the  whole  is 
gradually  warmed.  3.  The  cold  air  should  be  taken  from 
without  the  house,  and  not  from  an  entry  or  cellar,  because 
changing  the  air  of  those  places  in  winter,  is  apt  to  reduce  them 
to  a  freezing  temperature.  The  external  opening  should  be 
guarded  with  a  wire  net,  to  exclude  leaves  and  light  substances, 
and  the  internal,  should  be  commanded  by  a  shutter,  to  regu- 
late the  heat.  For  safety  it  is  best,  though  not  always  neces- 
sary, that  the  hot  air  passage  should  not  be  in  contact  with  the 
woodwork  of  the  house.  4.  Good  soapstone  is  the  best  mate- 
rial for  these  fire  places,  and  with  careful  use  will  last  many  years. 
See  Soapstone.  For  wood  fires,  the  stone  should  be  an  inch 
and  a  half  thick,  and  for  coal  fires,  two  or  three  inches. 

In  Plate  VIII.  Fig.  2,  is  a  section  of  a  double  fire  place.  A, 
is  the  place  of  the  fire,  H,  the  soapstone  back,  B,  the  throat, 
C,  the  chimney,  E,  the  external  opening,  D  G  G,  the  hollow, 
or  passage  for  heated  air,  M,  a  pipe  for  conveying  the  hot  air 
to  N,  a  lateral  opening  into  the  room.  P,  the  mantel  piece. 
A  soapstone  fire  place  may  be  rendered  very  effectual,  by  caus- 
ing it  to  project  a  little  into  the  room,  and  by  adding  an  air  box 
to  the  top,  as  seen  in  PI.  VIII.  Fig.  3  and  4.  In  the  section, 
Fig.  3,  A,  is  the  fire,  B  B,  the  smoke  passage,  C  c  c,  the  air 
passage,  D,  a  box  for  heated  air  covering  the  fire  place,  and 
communicating  with  the  hollow  back  c  c,  by  a  side  passage  at 
the  dotted  lines,  E,  a  side  opening  for  discharging  the  hot  air 
into  the  room,  G,  the  mantel  piece.  In  fire  places  of  cheap 
construction,  a  simple  hollow  back,  made  by  one  slab  of  soap- 
stone,  with  openings  as  have  been  described,  will  contribute 
much  to  increase  the  warmth  of  the  room. 

Coal  Grate. — When  coals  are  used  for  fuel,  it  is  necessary, 
on  account  of  their  small  size,  to  confine  them  together  with  a 
grate.  As  they  contain  more  combustible  matter,  in  the  same 
space,  than  wood,  and  produce  a  greater  degree  of  heat ;  a 
much  smaller  fire  place  answers  for  them.  A  very  small  throat 
21 


162 


ARTS  OF  HEATING  AND  VENTILATION. 


also  in  the  chimney,  is  sufficient  to  carry  off  the  smoke  from  a 
common  coal  grate.  With  this  exception  it  has  the  same 
characteristics  as  a  common  fire  place. 

Anthracite  Grate. — ^Orates  for  burning  anthracite,  require 
more  perpendicular  height,  than  others,  and  should  be  of  such 
a  proportionate  depth  as  will  keep  the  coal  together,  and  not 
offer  too  great  a  surface  to  the  atmosphere.  In  extremely  cold 
weather,  it  is  observed  that  the  front  surface  of  anthracite  grows 
black  and  burns  feebly  in  an  open  grate,  while  it  does  not  in  a 
furnace  or  stove.  In  this  case,  the  cold  air  conducts  off  the 
heat  of  the  surface,  faster  than  the  combustion  renews  it ;  and 
if  the  amount  of  surface  be  too  great  in  proportion  for  that  of 
the  solid  contents,  the  fire  will  go  out.  Anthracite  grates  are 
usually  provided  with  a  very  narrow  throat,  to  carry  off  the 
gases  which  result  from  the  combustion ;  there  being  no  visible 
smoke.  The  throat,  however,  should  always  be  large  enough 
to  transmit  the  smoke  of  any  other  fuel ;  for  otherwise,  a  part 
of  the  carbonic  acid  which  is  formed,  will  escape  into  the  room, 
and  contaminate  the  atmosphere,  in  the  same  way  as  burning 
charcoal.    See  Chap.  I.  art.  Anthracite. 

Burns''  Grate. — Mr  Burns,  of  Glasgow,  has  made  an  altera- 
tion in  the  coal  grate,  by  introducing  the  external  air  through 
on  opening  immediately  under  the  grate.  This  air  supphes  the 
fuel  with  oxygen,  and  furnishes  most  of  the  current  which  pass- 
es up  the  chimney.  The  air  of  the  room  of  course  remains 
comparatively  stationary,  and  is  sooner  heated.  This  plan,  when 
combined  with  the  double  fire  place,  already  mentioned,  [PI. 
VIII.  Fig.  3  and  4]  is  a  powerful  mode  of  obtaining  heat.  A 
moveable  stone  screen  should  be  placed  in  front  of  the  ash  pit, 
to  prevent  the  ashes  from  being  blown  into  the  room.  The  ex- 
ternal opening  which  admits  the  air,  should  not  be  near  any 
wood  work,  as  sometimes  the  current  is  reversed  by  winds,  and 
sparks  and  smoke  are  driven  out  at  the  opening. 

Building  a  Fire. — In  building  and  maintaining  an  open  fire, 
whether  of  wood  or  coal,  certain  circumstances  deserve  atten- 
tion, in  the  common  fire  places.    It  is  advantageous  to  make 


ARTS   OF  HEATING  AND  VENTILATION. 


163 


the  perpendicular  height  of  the  fuel,  as  great  as  is  consistent 
with  safety.  A  stratum  of  coals,  or  ignited  wood,  will  radiate 
more  heat  into  the  lower  part  of  the  room,  if  placed  vertically, 
than  if  laid  horizontally.  Fuel,  for  economy,  should  be  so  sub- 
divided, as  to  be  easy  of  ignition,  and  so  placed  as  to  give  free 
access  for  the  air  to  its  different  surfaces.  In  this  way  the  smoke 
is  more  likely  to  be  burnt.  To  secure  the  greatest  effect  of  ra- 
diation, the  combustion  should  be  kept,  as  much  as  possible,  to 
the  front  surface.  In  kindling  a  fire,  the  live  coals  should  be  kept 
together,  and  placed  near  the  bottom.  A  blower,  added  to  a 
common  grate,  converts  it  for  the  time  being,  into  a  wind  furnace. 

Furnaces. — The  object  of  the  furnaces  used  by  artists  and 
manufacturers,  is  the  reverse  of  that  intended  to  be  produced 
by  stoves  and  fire  places  ;  furnaces  being  required  to  produce 
an  intense  heat,  and  to  confine  it  to  a  limited  space.  Hence 
furnaces  and  their  chimneys  are  surrounded  with  nonconduc- 
tors, that  they  may  expend  as  little  of  their  heat,  as  possible,  on 
the  air,  and  surrounding  objects.  They  are  commonly  made 
of  fire  proof  bricks,  and  when  small,  are  inclosed  in  iron. 
Their  most  simple  form  is  that  of  an  upright,  hollow  cylinder, 
with  a  grate  at  bottom.  Air  or  wind  furnaces,  have  their  com- 
bustion supported  by  a  draught  of  air,  which  ascends  rapidly 
because  it  is  strongly  heated  and  rarified.  Blastfurnaces  have 
the  air  driven  through  their  fuel  with  bellows.  Reverberating 
furnaces  are  provided  with  a  concave  covering,  which  reverbe- 
rates, or  throws  back  the  flame,  upon  the  substances  to  be  heat- 
ed or  melted.  There  are  some  cases  in  which  furnaces  are 
used  for  warming  dwelling  houses,  particularly  when  fuel  is  used 
which  requires  strong  ignition,  such  as  the  Anthracites: 

Stoves. — Stoves  differ  from  fire  places  by  inclosing  the  fire 
so  as  to  exclude  it  from  sight,  the  heat  being  given  out  through 
the  material  of  which  the  stove  is  composed.  The  common 
Holland  stove,  of  which  we  have  an  almost  infinite  variety  of 
modifications,  is  an  iron  box  of  an  oblong  square  form,  intend- 
ed to  stand  in  the  middle  of  a  room.  The  air  is  admitted  to 
the  fire  through  a  small  opening  in  the  door,  and  the  smoke 


164 


ARTS  OF  HEATING  AND  VENTILATION. 


passes  off  through  a  narrow  funnel.  The  advantages  of  this 
stove  are — 1.  That  being  insulated  and  detached  from  the 
walls  of  the  room,  a  greater  part  of  the  heat  produced  by  the  com- 
bustion is  saved.  The  radiated  heat  being  thrown  into  the  walls 
of  the  stove,  they  become  hot,  and  in  their  turn  radiate  heat 
on  all  sides  to  the  room.  The  conducted  heat  is  also  received 
by  successive  portions  of  the  air  of  the  room  which  pass  in 
contact  with  the  stove.  2.  The  air  being  made,  as  in  furnaces, 
to  pass  through  the  fuel,  a  very  small  supply  is  sufficient  to  keep 
up  the  combustion,  so  that  httle  need  be  taken  out  of  the  room. 
3,  The  smoke  being  confined  by  the  cavity  of  the  stove,  can- 
not easily  escape  into  the  room,  and  may  be  made  to  pass  off 
by  a  small  funnel,  which,  if  sufficiently  thin  and  circuitous, 
may  cause  the  smoke  to  part  with  a  great  portion  of  its  heat, 
before  it  leaves  the  apartment.  These  circumstances  render 
the  Holland  stove  one  of  the  most  powerful  means  we  can  em- 
ploy for  keeping  up  a  regular  and  effectual  heat,  with  a  small 
expense  of  fuel. 

The  disadvantages  of  these  stoves  are,  that  houses  contain- 
ing them  are  never  well  ventilated,  but  that  the  same  air  remains 
stagnant  in  a  room  for  a  great  length  of  time.  Hence  it  neces- 
sarily becomes  impure  by  the  breath  of  persons  who  remain  in 
it,  and  by  the  burning  of  dust  and  other  substances  which  settle 
on  the  heated  iron  of  the  stove.  A  dryness  of  the  air  is  also  pro- 
duced, which  is  oppressive  to  most  persons,  so  that  it  often  be- 
comes necessary  to  place  an  open  vessel  of  water  on  the  stove, 
the  evaporation  of  which,  may  supply  moisture  to  the  atmos- 
phere. Where  rooms  are  kept  very  warm  by  stoves,  it  is  found 
advanta-geous  even  to  cause  the  water  to  boil,  in  order  to  insure 
a  sufficient  supply  of  vapor.  Stoves  are  very  useful  in  large 
rooms,  which  are  frequented  occasionally,  but  not  inhabited 
constantly  ;  as  halls,  churches,  he.  But  for  common  rooms, 
which  are  occupied  at  all  times,  they  are  objectionable,  for  the 
reasons  which  have  been  stated. 

Russian  Stove. — In  cold  countries,  where  it  is  desirable  to 
obtain  a  comfortable  warmth,  even  at  the  sacrifice  of  other 


ARTS   OF   HEATING   AND  VENTILATION. 


166 


conveniences,  various  modifications  of  the  common  stoves  have 
been  introduced,  to  render  them  more  powerful,  and  their  heat 
more  effectual.  The  Swedish  and  Russian  stoves  are  small 
furnaces,  with  a  very  circuitous  smoke  flue.  In  principle,  they 
resemble  a  common  stove  with  a  funnel  bent  round  and  round, 
until  it  has  performed  a  great  number  of  turns  or  revolutions 
before  it  enters  the  chimney.  It  differs,  however,  in  being 
wholly  enclosed  in  a  large  box  of  stone  or  brick  work,  which 
is  intersected  with  air  pipes.  In  operation  it  communicates 
heat  more  slowly,  being  longer  in  becoming  hot,  and  also  slow- 
er in  becoming  cold,  than  the  common  stove.  Russian  stoves 
are  usually  provided  with  a  damper,  or  valve,  at  top,  which  is 
used  to  close  the  funnel  or  passage,  when  the  smoke  has  ceas- 
ed to  ascend.  Its  operation,  however,  is  highly  pernicious, 
since  burning  coals,  when  they  have  ceased  to  smoke,  always 
gives  out  carbonic  acid  in  large  quantities,  which,  if  it  does  not 
escape  up  chimney,  must  deteriorate  the  air  of  the  apartment, 
and  render  it  unsafe. 

Cockle. — The  name  of  cockle  is  given  to  an  upper  part  of 
a  stove  or  furnace,  resembling  an  inverted  vessel.  A  large 
cockle  saves  much  heat,  since  its  extensive  surface  conveys  the 
heat  from  the  flame  and  smoke,  and  communicates  it  to  the  at- 
mosphere. In  some  stoves,  the  cockle  is  filled  with  a  chequer 
work  of  bricks,  among  which  the  smoke  and  flame  circulate. 
After  becoming  once  heated,  these  bricks  are  slow  in  cooling, 
and  continue  to  yield  warmth  to  the  apartment,  like  the  Russian 
stoves,  for  some  time  after  the  fire  is  extinguished. 

Cellar  Stoves  and  Air  Flues. — Such  is  the  tendency  of 
heated  or  rarified  air  to  ascend,  that  buildings  may  be  effectu- 
ally warmed  by  air  flues  communicating  with  stoves  in  the  cel- 
lar, or  any  part  of  the  building  below  that  to  be  warmed.  A 
large  suite  of  apartments  may  be  sufficiently  heated  in  this  way 
by  a  single  stove.  The  stove  for  this  purpose,  should  be  large 
and  of  a  kind  best  adapted  to  communicate  heat.  It  should  be 
entirely  enclosed  in  a  detached  brick  chamber,  the  wall  of  which 
should  be  double,  that  it  may  be  a  better  nonconductor  of  heat. 


166  ARTS  OF  HEATING  AND  VENTILATION. 

The  space  between  the  brick  chamber  and  stove  should  not 
exceed  an  inch.  In  the  apparatus  of  the  Derbyshire  and 
Wakefield  Infirmaries,  which  has  been  imitated  in  this  country, 
the  whole  of  the  air  is  repeatedly  conducted  by  numerous  pipes 
within  half  an  inch  of  the  stove  and  its  cockle.  For  the  supply 
of  fuel,  the  same  door  which  opens  into  the  chamber,  should 
open  also  into  the  stove,  that  there  may  never  be  any  commu- 
nication with  the  air  of  the  cellar.  A  current  of  external  air 
should  be  brought  down  by  a  separate  passage  and  delivered 
under  the  stove.  A  part  of  this  air  is  admitted  to  supply  the 
combustion  ;  the  rest  passes  upward  in  the  cavity  between  the 
hot  stove  and  the  wall  of  the  brick  chamber,  and  after  becom- 
ing thoroughly  heated,  is  conducted  through  passages  in 
which  its  levity  causes  it  to  ascend,  and  be  delivered  into  any 
apartment  of  the  house.  Difibrent  branches  being  established 
from  the  main  pipe,  and  commanded  by  valves  or  shutters,  the 
hot  air  can  be  distributed  at  pleasure,  to  any  one  or  more  rooms 
at  a  time.  This  plan  is  very  useful  in  large  buildings,  such  as 
manufactories,  hospitals,  he.  on  account  of  the  facility  with 
which  the  same  stove  may  be  made  to  warm  the  whole,  or  any 
part  of  them.  The  advantage  of  a  long  vertical  draught  ena- 
bles us  to  establish  a  more  forcible  current  of  warm  air.  See 
page  173.  The  rooms,  while  they  are  heated,  are  also  ventilated, 
for  the  air  which  is  continually  brought  in  by  the  warm  pipes, 
displaces  that  which  was  previously  in  the  room,  and  the  air 
blows  out  at  the  crevices  and  key  holes,  instead  of  blowing  in, 
as  it  does  in  rooms  with  common  fire  places. 

Heating  by  Steam. — Steam  is  found  to  be  a  useful  me- 
dium for  communicating  heat  to  large  buildings.  It  has  the 
advantage  that  it  conveys  heat  in  any  direction,  horizontally, 
upward,  or  downward,  and  to  the  most  remote  apartments  of 
the  largest  buildings.  In  green-houses  it  has  been  made  to 
yield  a  sufficient  supply  of  heat,  at  the  distance  of  800  feet 
from  the  boiler  in  which  it  is  produced.  *    When  steam  of  low 

^  At  Messrs  Loddigcs,  at  Hackney.    Tredgold,  on  Warming,  &c.  p.  19. 


ARTS   OF   HEATIN^   AND  VENTILATION. 


167 


pressure  is  employed,  the  heat  never  exceeds  212  degrees 
of  Fahrenheit,  so  that  the  air  in  contact  with  the  apparatus,  is 
never  contaminated  by  the  burning  of  dust. 

In  constructions  for  heating  by  steam,  a  strong  boiler  is  made 
use  of,  provided  with  a  safety  valve,  and  the  other  appendages 
common  to  the  boilers  of  steam  engines.  From  this  boiler  a 
steam  pipe  is  carried  in  any  required  direction,  and  distributes 
^  branches  to  the  different  apartments  which  are  to  be  warmed. 
Whenever  the  water  in  the  boiler  is  heated  to  the  point  of 
ebullition,  steam  passes  into  the  pipes  and  drives  out  the  atmos- 
pheric air  through  valves  provided  for  the  purpose.  As  long 
as  the  surface  of  the  pipes  remains  of  a  less  heat  than  212  de- 
grees, a  part  of  the  steam  continually  condenses,  and  is  imme- 
diately succeeded  by  fresh  steam  from  the  boiler.  In  the  act 
of  condensing,  its  gives  out  its  latent  heat  to  the  material  of 
which  the  pipe  is  made,  and  this  material,  in  turn,  imparts  it  to 
the  air  of  the  room.  In  this  manner  the  steam  will  continue  to  be 
condensed,  and  to  give  out  heat,  as  long  as  the  air  of  the  room  is  at 
any  point  below  212  degrees.  By  tlie  condensation,  a  quantity  of 
water  is  constantly  formed,  which,  for  economy  of  heat,  is  re- 
turned by  a  separate  pipe,  while  it  is  yet  warm,  to  the  boiler. 
Inverted  syphons  containing  water,  are  used  to  prevent  the  air 
and  steam  from  communicating.  If  the  steam  pipes  are  made 
of  thin,  or  weak  materials,  it  is  necessary  to  provide  them  with 
safety  valves 'opening  inward  ;  otherwise  they  would  be  crush- 
ed by  the  pressure  of  the  atmosphere,  when  the  fire  is  extin- 
guished. 

In  calculating  the  effect  of  this  method,  it  has  been  ascer- 
tained that  under  favorable  circumstances,  one  cubic  foot  of 
boiler  will  heat  about  2000  cubic  feet  of  space  in  a  cotton  mill, 
where  the  required  temperature  is  from  70  to  80  degrees  of 
Fahrenheit.*  .  And  if  we  allow  25  cubic  feet  of  a  boiler  for 
one  horse's  power,  in  a  steam  engine  supplied  by  it,  it  will  fol- 
low, that  such  a  boiler  is  adequate  to  warm  50,000  cubic  feet 


*  Buchanan  on  Heat  and  Fuel,  p.  160. 


168  ARTS   OF   HEATING   AND  VENTILATION. 

of  space  for  every  horse's  power.  It  is  said  also  that  every 
square  foot  of  surface  in  a  steam  pipe,  will  warm  200  cubic 
feet  of  space.  These  calculations,  however,  do  not  apply  to 
buildings  unfavorably  arranged,  nor  to  very  cold  weather.  The 
pipes,  employed  to  distribute  the  steam,  should  be  made  of 
materials,  which  cool  most  rapidly.  Iron,  of  which  the  surface 
is  tarnished  with  rust,  is  found  to  exceed  tinned  iron,  in  the  ra- 
pidity of  cooling,  in  the  proportion  of  about  18  to  10.  *  Room 
must  be  allowed  for  the  expansion  of  the  pipes,  which  in  cast 
iron  may  be  taken  at  a  tenth  of  an  inch  for  every  ten  feet  in 
length.  In  cotton  and  calico  manufactories,  steam  is  found 
very  advantageous  in  drying  cloths  quickly  and  well. 

In  comparing  the  effect  of  steam  heat,  with  that  of  smoke  flues, 
different  representations  have  been  made  by  writers  on  the  sub- 
ject. Mr  Tredgold  observes  that  'he  must  be  a  novice  in  the 
science  of  heat,  who  cannot  produce  nearly  the  same  effect  by 
the  one,  as  by  the  other,  all  other  circumstances  being  the  same.' 
The  steam  apparatus,  however,  requires  more  careful  manage- 
ment, and  does  not  admit  of  neglect.  Although  easily  kept  in 
order  by  a  skilful  attendant,  yet  it  cannot,  in  common  cases,  be 
entrusted  to  ordinary  or  careless  persons. 

RETENTION  OF  HEAT. 

Causes  of  Loss. — However  advantageously  heat  may  be 
produced  and  distributed,  it  will  fail  in  producing  its  desired 
effect,  unless  suitable  provision  is  made  for  retaining  it,  where 
it  is  wanted.  Heat  constantly  tends  to  an  equilibrium,  and,  un- 
less this  tendency  be  retarded,  dwelling  houses  and  their  apart- 
ments will  cool,  as  fast  as  they  are  warmed.  The  chief  causes 
which  operate  to  cool  apartments,  are — 1.  The  escape  of  the 
warm  air  upward,  through  crevices,  apertures,  and  chimnies. 
2.  The  power  of  conducting  and  of  radiating  heat,  which  all 
substances  possess  in  a  greater  or  less  degree,  and  by  which 


*  Tredgold,  p.  58. 


ARTS   OF  HEATING   AND  VENTILATION. 


169 


the  internal  heat  of  houses  is  gradually  conveyed  to  the  exter- 
nal atmosphere.  To  obviate  the  first  of  these  causes,  apart- 
ments should  be  made  as  tight  as  possible ;  and  to  prevent  the 
second,  at  least  in  part,  their  walls  should  be  made  thick,  and 
of  materials  which  are  slow  conductors  of  heat. 

Crevices. — As  crevices  in  rooms  commonly  occur  from  the 
shrinking  of  their  materials,  care  should  be  taken  to  employ,  in 
building,  wood  which  is  thoroughly  seasoned,  and  which  is 
known  to  be  permanent  in  its  dimensions.  Of  the  kinds  of 
wood  employed  for  doors  and  windows,  mahogany  is  the  most 
permanent,  and  next  to  this  is  pine.  Oak,  and  some  other  hard 
woods,  are  very  liable  to  shrink  and  crack. 

Chimriies. — Chimnies  occasion  less  expenditure  of  warm  air 
from  rooms,  than  their  size  would  lead  us  to  expect,  because 
they  open  at  the  bottom,  or  near  the  floor.  If,  therefore,  the 
room  be  tight,  and  the  chimney  cold,  the  warm  air,  while  at 
rest,  will  be  retained  in  the  upper  portion  of  the  room,  or  that 
which  is  above  the  fire  place,  as  effectually  as  in  a  gasometer. 
But  if  a  chimney  is  heated,  and  a  current  thus  established 
through  it,  it  may  then  drain  off  the  air  of  the  apartment ;  and 
hence  the  foundation  for  the  common  belief  that  a  room  becomes 
colder  in  the  night,  for  having  had  a  fire  in  the  day.  The  warm 
air  may  be  retained,  if  the  throat  of  the  fire  place  be  closed 
with  a  damper. 

Entries  and  Skylights. — Entries,  as  they  are  commonly  con- 
structed, extending  from  the  bottom  of  a  house  to  the  top, 
have  a  bad  influence  on  the  retention  of  heat.  The  evil  is  in- 
creased, when  they  are  surmounted  with  a  skylight,  the  panes 
of  which  are  arranged  like  tiles,  and  not  air  tight.  Such  en- 
tries are  difficult  to  warm,  and  serve  to  drain  off  the  warm  air 
of  apartments,  whenever  the  communicating  doors  are  left 
open ;  and  to  transmit  it  to  the  roof.  *    To  prevent  this  effect, 

*  The  opposite  currents  in  an  open  door,  by  which  cold  air  enters  at  bottom, 
and  warm  air  escapes  at  top,  maybe  made  obvious,  in  the  familiar  experiment 
of  holding  a  lighted  candle  at  the  bottom  and  top  of  the  door.    In  one  case 
the  flame  will  point  into  the  room,  and  in  the  other  out  of  it. 
22 


170 


ARTS   OF   HEATING  AND  VENTILATION. 


entries  should  be  commanded  with  doors  in  different  stories ; 
and  skylights  should  be  made  sufficiently  erect,  to  have  their 
sashes  complete,  or  else  a  tight  horizontal  window  should  be 
added  underneath  the  skylight. 

Windows. — The  heat  conducted  off  by  the  external  atmos- 
phere, passes,  most  readily,  through  the  windows  ;  since,  the 
walls  of  houses,  especially  when  thick,  are  slow  in  conducting 
caloric,  while  a  pane  of  glass  interposes  but  a  slight  barrier 
against  its  escape.  On  this  account  the  unnecessary  multipli- 
cation of  windows  should  be  avoided.  In  cold  chmates,  a  great 
advantage  is  obtained  from  using  double  windows  in  winter, 
which,  by  confining  between  them  a  stratum  of  air,  interpose  a 
powerful  nonconductor  between  the  room  and  the  atmosphere. 
To  secure  the  full  benefit  of  the  double  window,  it  should  be 
made  as  tight  as  possible,  so  that  the  included  stratum  of  air 
may  not  easily  change  ;  otherwise  the  expected  benefit  will  not 
be  obtained. 


VENTILATION. 

Objects. — If  the  only  object  of  human  habitations  were  to 
procure  heat,  it  would  be  best  obtained  by  keeping  the  air  in  a 
state  of  stagnation,  and  employing  those  means  to .  create 
warmth,  which  are  attended  with  the  least  circulation,  or  change. 
But  since  the  air  of  inhabited  rooms  w^ould  become  in  time  un- 
fit for  respiration,  it  is  necessary  that  it  should  be  removed,  as 
fast  as  deteriorated,  and  be  replaced  by  fresh  air  from  abroad. 

Rooms  which  are  heated  with  stoves  are  never  well  ven- 
tilated. Those  heated  by  common  fire  places,  are  ven- 
tilated, at  the  expense  of  losing  much  of  their  warmth  by  the 
admission  of  cold  air.  Those  heated  by  the  double  fire  place 
[p.  160],  are  sufficiently  ventilated,  with  air  at  an  agreeable 
temperature.  Rooms  heated  by  steam  are  not  at  all  ventilated, 
unless  it  be  by  additional  arrangements.  Those  w^armed  by 
hot  air  flues  are  apparently  well  ventilated,  yet  in  hospitals  and 


ARTS   OF   HEATING   AND  VENTILATION. 


171 


crowded  buildings,  it  is  sometimes  necessary  to  add  fire  places, 
or  other  openings,  for  discharging  the  air. 

Ventilators. — The  principal  gases,  which  it  is  the  object 
of  ventilation  to  remove,  are  carbonic  acid  and  nitrogen; 
these  being  produced  in  excess  by  the  process  of  respiration, 
by  the  combustion  of  lamps,  and  by  fires  with  an  imperfect 
draught.  The  specific  gravity  of  carbonic  acid  is  greater 
than  that  of  common  air.  That  of  nitrogen  is  somewhat 
less.  These  gases  when  evolved,  are  at  an  higher  tempe- 
rature than  the  surrounding  air,  and  are  mixed  with  steam ; 
therefore,  while  rarified  by  heat,  they  ascend  to  the  top  of  the 
apartment.  On  this  account  the  ventilators  intended  to  dis- 
charge them,  are  m.ade  to  consist  of  openings,  commanded  by 
shutters,  at  the  upper  part  of  the  room.  In  rooms  which  are 
liable  to  be  crowded  with  people,  these  ventilators  have  a  good 
effect,  especially  in  warm  weather,  and  the  larger  they  are,  the 
greater  is  the  advantage  derived  from  them.  In  cold  weather, 
however,  they  have  the  disadvantage  that  they  discharge  the 
pure  heated  air,  in  common  with  the  noxious  vapors,  and  thus 
defeat  our  efforts  to  obtain  warmth.  In  common  dwelling 
houses,  no  more  ventilation  is  necessary,  than  can  be  obtained 
from  doors,  open  fire  places,  and  windows  which  open  at  top, 
as  well  as  at  bottom. 

Culverts. — In  the  Derbyshire  Infirmary  an  ingenious  mode 
of  ventilation  is  adopted,  by  means  of  an  empty  culvert,  or  sub- 
terranean passage ;  one  end  of  which  opens  into  the  building, 
while  the  other  end  is  provided  with  a  turncap  presenting  its 
open  mouth  to  the  wind.  The  air,  in  passing  this  culvert,  par- 
takes of  the  temperature  of  the  earth,  and  is  thus  warmed  in 
winter,  and  cooled  in  summer.  The  effect,  however,  is  obvi- 
ously of  a  limited  kind,  siilce  the  continual  transmission  of  air 
must  bring  the  surface  of  the  culvert,  to  a  temperature  ap- 
proaching that  of  the  surface  of  the  ground. 

Smoky  Rooms. — Under  the  head  of  ventilation  may  be 
placed  the  art  of  remedying  smoky  apartments.  Smoke  is  a 
heterogeneous  vapor,  composed  of  the  gases  which  result 


172 


ARTS  OF  HEATING  AND  VENTILATION. 


from  combustion,  together  with  a  quantity  of  opaque  matter, 
which  escapes  from  the  fuel  without  being  burnt.  Smoke  is 
specifically  heavier  than  the  atmosphere,  and  always  descends 
after  it  is  cooled,  as  may  be  seen  by  observing  the  current  of 
smoke  from  a  chimney  in  a  cold  morning.  At  the  time  how- 
ever of  its  disengagement  from  the  fire,  it  is  rarified  by  heat, 
and  will  always  ascend  through  a  chimney  properly  construct- 
ed, if  it  is  not  prevented  by  some  opposing  influence.  The 
causes  which  produce  smoky  apartments  are  principally  the 
following. 

Damp  Chimnies. — When  a  fire  is  first  made  in  a  chimney, 
which  has  not  been  used  for  many  months,  it  is  apt  to  smoke. 
This  is  because  the  chimney  is  cold,  and  the  column  of  air 
which  it  contains  is  not  lighter  than  the  surrounding  atmosphere. 
The  difficulty  of  remedying  this  evil  is  greater,  if  the  bricks 
have  absorbed  much  moisture,  or  the  chimney  be  new ;  as  in 
this  case  the  chimney  will  not  be  well  heated,  till  the  moisture 
is  evaporated.  To  expedite  the  drying  and  heating  of  the 
chimney,  a  window  should  be  kept  open  on  the  side  against 
which  the  wind  blows,  and  the  communication  with  the  rest  of 
the  house,  at  the  same  time,  closed.  This  will  mechanically 
assist  the  smoke  and  hot  air  in  ascending  the  chimney. 

Large  Fire  Places. — If  a  fire  place  be  made  too  high,  it  will 
be  liable  to  smoke,  for,  since  the  throat  of  the  chimney  takes  in 
air  from  all  directions,  if  the  fire  be  too  remote  from  this  point, 
its  smoke  will  be  less  likely  to  find  its  proper  way.  On  the 
other  hand,  the  lower  the  mantel  piece  is  brought,  the  nearer 
will  the  fire  place  approach  to  the  character  of  a  wind  furnace. 
In  like  manner  if  the  throat  of  the  fire  place  be  too  large,  the 
air  of  the  room,  as  well  as  that  of  the  fire,  will  pass  freely  up 
the  chimney,  and  thus  the  whole  included  air  being  colder,  its 
current  will  be  more  sluggish.  The  advanced  back  of  the 
Rumford  fire  place,  by  contracting  the  throat,  remedies  this 
difficulty ;  and  at  the  same  time  presents  a  mechanical  obstacle 
against  sudden  counter  currents. 


ARTS   OF   HEATING  AND  VENTILATION. 


173 


Close  Rooms. — Closeness  of  a  room  is  a  cause  of  its  being 
smoky.  If  the  walls,  doors,  and  windows,  are  air  tight,  or  near- 
ly so,  the  outer  air  cannot  enter  to  take  the  place  of  that  which 
passes  up  the  chimney.  The  current  of  heated  air  and  smoke 
will  therefore  be  interrupted  and  expand  into  the  room.  In 
most  rooms  it  happens  that  the  crevices  occasioned  by  the 
shrinking  of  the  wood,  or  by  the  want  of  exactness  in  finishing, 
admit  air  enough,  and  more  than  enough,  to  supply  the  chimney. 
In  new  apartments,  however,  where  all  the  joinings  have  been 
made  with  great  accuracy,  it  has  been  found  necessary  to  make 
perforations  in  the  walls  to  admit  air  sufficient  to  keep  up  a 
current.  These  should  always  be  made  behind  the  back  of 
the  fire  place,  when  possible,  for  reasons  already  explained. 

Contiguous  Doors. — The  doors  of  a  room,  if  placed  very 
near  a  fire  place,  or  on  the  same  side  of  the  room  with  it,  are  apt 
to  occasion  a  smoke,  as  often  as  they  are  opened.  The  gust 
of  air  which  enters  at  an  open  door  so  situated,  blows  across 
the  chimney.  A  part  of  it  ascends  the  flue,  while  the  rest  ex- 
tends into  the  room  carrying  with  it  a  part  of  the  smoke. 

Short  Chimnies. — The  longer  a  chimney  is,  the  more  per- 
fect is  its  draught,  since  the  upward  tendency  is  proportionate 
to  the  difference  of  weight  between  the  column  of  air  included 
in  the  chimney,  and  a  similar  column  of  external  air.  Short 
chimnies  or  flues  are  liable  to  smoke  from  the  heated  passage 
not  being  long  enough  to  establish  a  strong  current.  The  fire 
places  in  upper  stories  are  more  apt  to  smoke  than  those  in  the 
lower  apartments.  In  low  houses,  outhouses,  Sic,  the  chim- 
ney should  always  be  carried  to  the  greatest  practicable  height. 
Two  flues  in  the  same  chimney  or  stack  should  not  communi- 
cate at  any  point  short  of  the  top. 

Opposite  Fire  Places. — When  two  chimnies  exist  in  differ- 
ent parts  of  the  same  room,  or  in  rooms  which  communicate 
by  doors,  it  is  difficult  to  kindle  a  fire  in  one,  while  the  other  is 
burning,  especially  if  the  room  be  tight ;  because  in  this  case 
the  fire  which  is  first  established,  feeds  itself  by  a  current  brought 
down  the  vacant  chinniey.    After  both  fires  are  kindled,  it  is 


474 


ARTS  OF  HEATING  AND  VENTILATION. 


necessary  to  keep  up  a  certain  equilibrium  between  them,  oth- 
erwise the  stronger  will  overpower  the  latter,  and  draw  down 
its  smoke  into  the  room.  If  doors  or  windows  be  opened,  the 
evil  is  obviated.  If  the  fires  are  in  different  rooms,  the  com- 
municating doors  between  them  should  be  shut. 

JVeighboring  Eminences. — The  vicinity  of  elevated  objects, 
such  as  hills,  precipices,  or  very  high  buildings,  is  productive 
of  smoky  rooms  to  houses  in  their  neighborhood.  When  the 
wind  blows  in  a  direction  from  the  elevated  object  to  the  house, 
it  falls  down  in  an  oblique  direction  upon  the  roof ;  a  part  of  it 
enters  the  chimney,  and  beats  down  the  smoke,  by  overpower- 
ing its  current.  On  the  other  hand  when  the  wind  sets  towards 
the  hill  or  elevated  object,  its  passage  becomes  obstructed,  and 
it  presses  in  every  direction  to  escape;  and  while  its  upper  por- 
tions pass  off  by  the  top  of  the  opposing  body,  the  lower  por- 
tions press  downward  through  any  passages  which  may  afford 
them  an  escape.  Chimnies  in  houses  thus  situated  should  be 
carried  up  to  a  great  height,  so  as,  if  possible,  to  overtop  the 
eminence,  their  sides  being  secured  by  iron  braces. 

Turncap,  &fc. — In  many  instances  a  turncap,  which  is  a  cur- 
ved tube  regulated  by  a  weathercock,  so  as  always  to  turn  its 
mouth  in  a  direction  from  the  wind,  will  prevent  smoking,  in  the 
case  last  stated.  The  turncap  offers,  also,  a  security  against 
the  influence  of  strong  winds,  which  in  common  cases  and  in 
houses  most  favorably  situated,  often  invert  the  course  of  the 
smoke  by  the  strong  pressure  they  exert  on  the  tops  of  chim- 
nies, and  by  impinging  against  their  inner  side.  In  like  man- 
ner the  pots,  which  are  frusta  of  cones  or  pyramids,  placed  on 
the  tops  of  chimnies,  assist  the  escape  of  smoke,  by  causing 
the  wind  to  glance  upward  from  their  sides. 

Contiguous  Flues. — ^When  two  chimnies  are  contiguous  to 
each  other,  or  in  the  same  stack,  one  is  frequently  liable  to 
smoke,  when  the  other  contains  a  fire,  from  a  variety  of  cir- 
cumstances. Not  only  the  effect  of  high  winds,  but  also  any 
circumstance,  which  tends  to  produce  an  inverted  current,  may 
bring  down  the  smoke  from  one  chimney  into  the  apartment 


ARTS   OF   HEATING  AND  VENTILATION. 


175 


which  contains  the  other.  To  prevent  this  evil,  the  fire  places 
should  be  furnished  with  dampers  which  can  be  closed  when 
the  flue  is  not  in  use. 

Burning  of  Smoke. — This  subject  has  excited  great  atten- 
tion, owing  to  the  nuisance  produced  by  smoke  in  large  cities 
and  manufacturing  towns,  chiefly  where  coal  is  burnt.  In  an 
economical  view  it  deserves  attention,  since  it  renders  the  same 
fuel  more  effective.  Several  methods  of  getting  rid  of  smoke 
have  been  proposed  and  executed  with  some  success.  The 
first  mode  is  to  cause  the  smoke  to  pass  through  a  portion  of  fuel 
which  is  perfectly  ignited  and  does  not  smoke,  and  which  if  ac- 
curately managed,  burns  it  up.  This  has  been  effected  by  an 
inverted  draught,  in  a  syphon  chimney,  and  also  by  a  revolving 
grate,  which  places  the  ignited  fuel  between  the  fresh  fuel  and 
the  chimney.  Another  mode  is  to  mix  a  current  of  fresh  air 
with  the  smoke,  which  causes  it  to  burn  upon  passing  in 
contact  with  a  clear  fire.  A  third  method  which  has  been 
adopted  for  disposing  of  smoke,  consists  in  building  chim- 
nies  of  an  extraordinary  height,  so  that  most  of  the  smoke  may 
be  deposited  in  soot  upon  their  sides.  It  has  also  been  propos- 
ed to  build  circuitous  chimnies,  in  one  part  of  which  the  smoke 
should  pursue  a  descending  course,  and  that  in  this  part  a  shower 
of  water  should  be  kept  up,  to  precipitate  the  denser  particles  of 
the  smoke.  The  expense  of  this  method  will  probably  pre- 
vent its  use,  unless  in  some  cases  to  get  rid  of  dangerous  me- 
tallic fumes  in  manufactories. 


Franklin's  Works  ; — Rumford's  Works ; — Tredgold,  on  Warm- 
ing and  Ventilating  Buildings,  8vo.  1824  ; — Buchanan,  on  the  Econo- 
my of  Fuel  and  Management  of  Heat,  8vo.  1810 ;— Sylvester's 
Philosophy  of  Domestic  Economy,  and  Account  of  the  Derbyshire  In- 
firmary, 4to. ; — Account  of  the  Wakefield  Asylum,  fol. ; — Brande's 
Quarterly  Journal,  No's  22,  24,  27,  37,  &c. 


CHAPTER  IX. 


ARTS  OF  ILLUMINATION. 

Flame. — Artificial  light  is  obtained  for  common  purposes,  by 
the  combustion  of  substances,  which  afford  a  permanent  and 
luminous  flame.  All  flames  are  not  equally  luminous.  Those 
substances  which,  during  combustion,  produce  chiefly  gaseous 
or  volatile  matter,  emit  from  their  flame  a  very  feeble  light,  as 
is  seen  in  burning  hydrogen,  or  sulphur.  Those,  on  the  other 
hand,  which  produce  particles  of  solid  matter  during  their  com- 
bustion, yield  a  whiter  flame,  and  a  greater  illumination.  Sir 
Humphrey  Davy  is  of  opinion  that  the  brilliancy  of  the  flames, 
used  for  illumination,  is  owing  to  the  decomposition  of  the  gas- 
eous matter  towards  the  interior  of  the  flame,  by  which  solid 
charcoal  is  produced,  and  strongly  ignited,  before  it  is  burnt. 
In  a  conical  flame,  like  that  of  a  candle,  the  combustion  takes 
place  most  rapidly  toward  the  surface,  where  the  inflammable 
gas  mixes  with  the  atmospheric  air.  At  the  centre  of  the  base, 
there  is  a  darker  portion,  which  consists  of  the  matter,  which 
is  volatilized,  but  not  yet  fully  on  fire.  In  the  interior,  or  most 
luminous  part,  the  solid  particles  are  brought  to  a  white  heat, 
just  before  they  are  burnt.  The  degree  of  their  ignition  is 
very  powerful,  since  it  is  found  that  the  flame  of  a  common 
candle  is  hot  enough  to  melt  a  small  filament  of  platinum. 

Support  of  Flame. — That  a  flame  may  burn  steadily,  and 
produce  a  uniform  light,  it  is  necessary  that  the  supply  of  com- 
bustible matter  should  be  constant  and  uniform.  For  this  pur- 
pose the  combustible  must  be  in  a  liquid,  or  gaseous  state, 
when  it  approaches  the  flame,  so  that  it  may  flow  in  an  uninter- 
rupted current.    This  current  is  commonly  sustained  either  by 


ARTS   OF  ILLUMINATION. 


177 


capillary  attraction,  or  by  mechanical  pressure,  operating  on  the 
reservoir  which  contains  the  combustible. 

Torches  and  Candles. — The  rudest  material  used  for  afford- 
ing light,  is  the  torch,  composed  of  the  resinous  part  of  wood 
of  the  pine  or  fir.  In  such  torches,  the  turpentine,  or  melted 
resin,  oozes  out  through  the  pores  of  the  wood,  and  is  gradually 
burnt,  the  wood  interposing  a  vehicle,  which  regulates  the  sup- 
ply and '  prevents  it  from  being  consumed  at  once ;  thus 
sustaining  a  dull  and  irregular  light,  with  much  smoke,  for  some 
time.  A  common  candle  is  an  improvement  upon  this  natural 
mechanism.  It  consists,  as  is  well  known,  of  a  fusible  solid, 
'as  tallow,  wax,  or  spermaceti,  formed  into  a  cylinder,  having  a 
wick  of  cotton,  or  some  other  porous  substance,  for  its  axis. 
As  the  tallow  melts  by  the  radiated  heat  of  the  flame,  it  is  car- 
ried upward  by  the  capillary  attraction  of  the  wick,  and  is  con- 
verted into  vapor  as  fast  as  it  reaches  the  surface.  The  end 
of  the  wick  although  it  is  blackened  by  the  heat,  is  prevented 
from  consuming,  merely  because  it  is  surrounded  by  inflamma- 
ble vapor,  so  that  the  oxygen  of  the  atmosphere  has  no  access 
to  it.  If  the  wick  be  turned  t6  one  side,  so  as  to  project  from 
the  blaze  into  the  atmospheric  air,  it  is  immediately  burnt  off. 
Tallow  being  more  fusible  than  wax,  requires  to  be  burnt  with 
a  larger  wick.  The  reason  why  this  wick  requires  continual 
snuffing  is,  that  if  it  is  suffered  to  become  long  it  divides  the 
blaze  and  intercepts  a  part  of  the  light,  it  also  cools  the  flame 
by  its  radiation,  obstructs  the  combustion,  and  thus  causes  the 
escape  of  smoke  and  the  deposition  of  charcoal.  Wax  and 
spermaceti,  being  less  fusible,  may  be  burnt  with  a  smaller  w^ick, 
which,  if  made  sufficiently  slender,  bends  out  of  the  flame  and 
burns  off,  so  as  not  to  require  snuffing. 

Lamps. — When  the  combustible  used  is  fluid  at  common 
temperatures,  a  vessel  is  necessary  to  contain  this  fluid  and  sup- 
ply it  to  the  flame.  In  this  country,  and  in  England,  whale  oil 
is  the  principal  fluid  which  is  burnt  in  lamps.  *    In  France  and 

*  The  oil  which  is  extracted  in  cold  weather,  and  called  winter  strained 
oil,  remains  fluid  at  low  temperatures.    The  summer  strained  oil  is  liable  to 

23 


178 


ARTS   OF  ILLUMINATION. 


the  south  of  Europe,  the  oil  of  poppies,  of  nuts,  rape  seed,  and 
the  inferior  kinds  of  olive  oil,  are  used  for  this  purpose.  The 
volatile  oils,  are  but  seldom  burnt,  since  they  exhale  a  strong 
odor  and  throw  off  soot  during  their  combustion.  They  are 
also  liable  to  take  fire  over  their  whole  surface,  unless  guarded 
with  great  care.  Naptha,  however,  as  it  is  found  native,  or  as 
it  is  distilled  from  pitcoal,  is  used  for  supplying  street  lamps  in 
some  of  the  cities  of  Europe. 

Reservoirs. — As  the  flame  of  a  lamp  is  intended  to  consume 
no  more  oil  than  is  attracted  upward  by  the  capillary  action  of 
the  wick,  it  is  necessary  that  a  sufficient  body  of  oil  should  be 
so  placed,  as  to  keep  its  surface  permanently  at  a  small  distance 
b'elow  the  level  of  the  flame.  The  Greeks  and  Romans  em- 
ployed lamps  of  various  forms,  having  the  wick  projecting  from 
a  sort  of  beak  at  the  side,  nearly  on  a  level  with  the  surface  of 
the  oil.  A  similar  plan  is  now  practised  in  our  street  lamps. 
At  the  present  day,  portable  lamps  of  small  size,  are  made 
with  a  central  wick,  having  the  reservoir  of  oil  immediately  be- 
low the  flame.  These  reservoirs,  if  small,  require  frequent  fill- 
ing, and  if  large,  cast  an  inconvenient  shadow.  All  closed 
lamps  require  a  minute  hole  for  the  admission  of  air,  otherwise 
the  pressure  of  the  atmosphere  will  prevent  the  oil  from  ascend- 
ing the  wick.  If  this  hole  be  obstructed,  the  oil  will  also  some- 
times overflow,  from  the  expansion  of  the  confined  air,  when 
heated. 

Astral  Lamp. — With  a  view  to  get  rid  of  the  effect  of  shad- 
ow, various  contrivances  have  been  introduced,  in  which  the 
reservoir  is  placed  at  a  distance  from  the  flame.  In  the  Astral 
and  Sinumbral  lamps,  the  principle  of  which  was  invented  by 
Count  Rumford,  the  oil  is  contained  in  a  large  horizontal  ring, 
having  a  burner  at  the  centre,  communicating  with  the  ring  by 
two  or  more  tubes  placed  like  rays.    The  ring  is  placed  a  little 

congeal  in  winter.  To  obviate  this  inconvenience,  lamps  have  been  contriv- 
ed for  melting  the  summer  oil  by  the  heat  of  the  blaze.  This  is  done  either 
by  placing  the  reservoir  of  oil  immediately  over  the  blaze,  or  by  conducting 
the  heat  by  a  metallic  bar  which  extends  from  the  flame  into  the  reservoir. 


ARTS   OF  ILLUMINATION. 


179 


below  the  level  of  the  flame,  and  from  its  large  surface  af- 
fords a  supply  of  oil  for  many  hours.  A  small  aperture  is  left 
for  the  admission  or  escape  of  air,  in  the  upper  part  of  the 
ring.  When  these  lamps  overflow,  it  is  usually  because  the 
ring  is  not  kept  perfectly  horizontal,  or  else  because  the  air  hole 
is  obstructed,  a  circumstance  which  may  even  happen  from  fill- 
ing the  lamp  too  high  with  oil. 

Hydrostatic  Lamps. — In  several  cases,  the  laws  of  hydros- 
tatics have  been  applied  to  raise  oil  to  the  flame  from  a  reser- 
voir placed  so  far  below  the  wick  as  to  be  out  of  the 
reach  of  its  effective  capillary  attraction.  One  of  these 
hydrostatic  lamps  is  constructed  on  the  principle  of  Hero's 
fountain.  It  is  composed  of  three  vessels  -or  D| 
cavities  occupying  different  heights  and  com- 
municating by  tubes  or  syphons.  One  por- 
tion of  oil  by  descending  gradually  from  the 
middle  vessel  A,  to  the  lower  vessel  B,  causes 
another  portion  of  oil  to  ascend  from  the  upper 
vessel  C,  to  the  flame  at  D,  the  hydrostatic 
equilibrium  being  kept  up  by  the  interven- 
tion of  the  column  of  air  B  C. 

The  lamps  of  Girard  de  Marselle,  and  of  King,  are  on  this 
principle,  though  the  form  of  their  apparatus  is  that  of  a  cylin- 
der, with  internal  tubes  opening  into  different  cavities. 

Other  hydrostatic  lamps  are  constructed,  so  as  to  contain,  in 
one  part,  a  column  of  some  fluid,  the  specific  gravity  of  which, 
is  considerably  greater  than  that  of  oil,  such  for  example  as 
water  saturated  with  sak.  This  fluid  acts  in  such  a  manner  as 
to  raise  the  oil,  by  its  greater  weight.  Thus  if  an 
inverted  syphon  contain  oil  in  one  part,  and  salt 
water  in  another,  the  surfaces  of  the  two  fluids 
will  stand  at  different  heights,  inversely  proportion- 
ate to  their  specific  gravities.  In  the  diagram.  A, 
represents  the  surface  of  the  heavier  fluid,  and  B, 
that  of  the  oil.  The  bulbs  serve  as  reservoirs  to  prolong  the 
action.     Mr  Kiers'  lamp  is  constructed  on  this  principle. 


180 


ARTS   OF  ILLUMINATION. 


Those  of  Barton  and  Edelkrantz  depend  on  the  same  princi- 
ple, but  in  their  construction,  an  open  tube  of  oil  is  made  to 
float  in  an  upright  vessel  containing  a  heavier  fluid,  which  in 
some  cases  is  salt  water,  in  others  mercury.  As  the  oil  con- 
sumes, the  tube,  with  the  wick  and  light,  descend  in  the  sup- 
porting fluid,  and  follow  the  surface  of  the  oil,  as  it  lowers. 

Automaton  Lamp. — The  automaton  lamp  of  Porter,  is  a 
simple  and  effectual  contrivance  for  keeping  the  surface  of  the 
oil  near  tlie  level  of  the  blaze.  It  consists  of  an  oblong  tin 
box,  having  the  wick  tubes  at  one  end,  this  end  being  thus  ren- 
dered heavier  than  the  other.  The  box  is  suspended  on  piv- 
ots placed  a  httle  out  of  the  centre,  and  toward  the  tubes,  so 
that  when  the  lamp  is  full  of  oil,  the  box  will  hang  level.  As 
the  oil  burns  out,  however,  the  end  containing  the  tubes  will 
preponderate,  so  as  to  keep  the  flame  always  near  the  surface 
of  the  oil.  The  annexed  figures  show  the  position  of  the  lamp 
when  full,  and  when  half  exhausted.  This  lamp  is  of  cheap 
construction,  and  is  said  to  be  extensively  used  in  cotton  mills 
and  other  manufactories  in  the  north  of  England. 


Mechanical  Lamps. — Some  lamps  are  manufactured  in 
France,  in  which  the  oil  is  raised  from  a  large  reservoir  below, 
to  a  small  one  near  the  flame,  by  means  of  a  pump.  This  in 
some  instances  is  worked  by  hand,  and  in  others  is  carried  by 
clock  work,  the  motion  being  derived  from  a  spring,  which  is 
wound  up  as  often  as  necessary. 

Fountain  Lamp. — The  most  common  mode  of  disposing  of 
the  oil  in  large  lamps,  is  to  place  the  reservoir  above  the  level 
of  the  flame,  so  that  the  burner,  or  part  containing  the  wick, 


ARTS   OF  ILLUMINATION. 


181 


may  be  supplied  in  small  quantities,  as  fast  as  its  oil  is  consum- 
ed. These  reservoirs  are  constructed  on  the  principle  of  the 
bird  fountain.  They  are  open  at  bottom,  but  the  oil  is  kept 
from  running  out  at  once,  by  the  pressure  of  the  atmosphere. 
The  reservoir  commonly  terminates  in  a  neck  at  bottom,  with 
an  opening  on  one  side.  This  neck  is  immersed  beyond  the 
opening,  in  a  small  cavity,  which  contains  oil  nearly  on  a  level 
with  the  burners,  and  communicates  with  them  by  tubes.  So 
long  as  the  whole  of  the  opening  is  immersed,  no  oil  can  de- 
scend from  the  reservoir,  because  no  air  can  enter  to  take  its 
place.  But  whenever  the  oil  in  the  lower  cavity  is  consumed 
so  far,  as  to  sink  below  the  upper  edge  of  the  opening,  a  bub- 
ble of  air  will  enter  the  neck  and  ascend  into  the  reservoir ;  at 
the  same  time  displacing  an  equal  bulk  of  oil,  w^hich  descends 
to  feed  the  lamp.  For  convenience,  the  opening  is  command- 
ed by  a  sliding  valve,  and  when  the  reservoir  is  to  be  filled,  it 
is  unscrewed  from  the  lamp,  inverted,  and  the  oil  poured  in  at 
the  neck.  When  these  lamps  overflow,  it  is  commonly  owing 
to  an  increase  in  the  heat  of  the  room,  w^hich  causes  the  air  in 
the  upper  part  of  the  reservoir  to  expand,  and  drive  out  a  por- 
tion of  oil.  As  it  is  not  easy  to  prevent  this  occurrence,  lamps 
are  usually  provided  with  receptacles  at  bottom  to  receive  the 
waste  oil  which  runs  over  at  the  wick. 

Argand  Lamp. — This  name  is  applied,  after  one  of  the  in- 
ventors, to  all  lamps  with  hollow  or  circular  wicks  ;  and  of 
course  most  of  the  lamps  already  described,  may  be  also  Ar- 
gand lamps,  if  furnished  with  a  circular  burner.  The  intention 
of  the  Argand  burner,  is  to  furnish  a  more  rapid  supply  of  air 
to  the  flame,  and  to  afford  this  air  to  the  centre,  as  w^ell  as  the 
outside  of  the  flame.  It  is  constructed  by  forming  a  hollow 
cylindrical  cavity,  which  receives  oil  from  the  main  body  of 
the  lamp,  and  at  the  same  time  transmits  air  through  its  axis, 
or  central  hollow.  In  this  cavity  is  placed  a  circular  wick,  at- 
tached at  bottom  to  a  moveable  ring.  This  ring  is  capable  of 
being  elevated  or  depressed  by  means  of  a  rack  and  pinion,  or 
more  commonly  by  a  screw ;  so  that  the  height  of  the  wick 


182 


ARTS   OF  ILLUMINATION. 


may  be  varied  to  regulate  the  size  of  the  flame.  On  the  out- 
side is  placed  a  glass  chimney,  which  is  capable  of  transmitting 
a  current  of  air,  on  the  same  principles  as  a  common  smoke 
flue.  When  this  lamp  is  lighted,  the  combustion  is  vivid,  and 
the  light  intense,  owing  to  the  free  and  rapid  supply  of  air. 
The  flame  does  not  waver,  and  the  smoke  is  wholly  consumed. 
The  brilliancy  of  the  light  is  still  further  increased,  if  the  air 
be  made  to  impinge  laterally  against  the  flame.  This  is  done 
either  by  contracting  the  glass  chimney  near  the  blaze,  so  as  to 
direct  the  air  inwards,  or  by  placing  a  metallic  button  over  the 
blaze,  so  as  to  spread  the  internal  current  outward. 

Reflectors. — For  obvious  reasons,  a  lamp  yields  most  availa- 
ble light,  when  it  is  placed  in  the  centre  of  a  room,  or  space  to 
be  illuminated.  In  this  situation,  if  a  reflecting  surface  be 
brought  near  to  it,  this  surface  by  its  reflection  will  increase  the 
amount  of  light  in  one  direction,  at  the  expense  of  intercepting 
it  in  another,  so  that  the  total  advantage  is  not  increased  by 
the  reflector.  But  when  a  lamp  is  placed  near  a  wall,  so  that 
a  part  of  its  rays  are  wasted  by  falling  immediately  upon  the 
wall,  in  this  case  if  a  polished  surface  be  placed  behind  the 
flame,  it  reflects  back  most  of  the  rays,  which  would  otherwise 
be  lost  upon  the  nonreflecting  wall ;  and  thus  it  increases  the  ef- 
fect of  the  light.  The  familiar  fact  that  rooms  with  light  col- 
ored walls  are  most  easily  lighted,  is  owing  to  the  greater  re- 
flective power  which  such  walls  possess,  when  compared  with 
darker  surfaces. 

Hanging  of  Pictures. — As  the  surface  of  varnished  paint- 
ings has  a  considerable  reflecting  power,  it  happens  that  when 
the  spectator  stands  in  the  way  of  the  reflected  light,  his  eye  is 
dazzled,  and  rendered  incapable  of  distinctly  perceiving  the 
picture.  Paintings,  therefore,  should  not  be  hung  opposite  to 
lights,  nor  in  any  situation  in  which  a  line  drawn  from  the  place 
intended  for  spectators  will  make  the  same  angle  with  the  sur- 
face of  the  picture,  as  a  line  drawn  from  a  window  or  other  il- 
luminating point ;  the  angle  of  reflection  being  always  equal 
to  the  angle  of  incidence.    As  a  general  rule,  a  picture  will  be 


ARTS   OF  ILLUMINATION. 


183 


in  a  bad  light  with  regard  to  a  spectator,  whenever  the  image 
of  a  window  could  be  seen  by  him  in  a  looking  glass  occupying 
the  same  place  as  the  picture. 

Transparency  of  Flame. — If  two  lamps  be  placed  by 
the  side  of  each  other,  the  flame  of  the  one,  when  clear  of 
smoke,  does  not  intercept  the  light  of  the  other,  and  casts  little 
or  no  shadow.  Count  Rumford  found  that  the  brilliancy  of 
flame  is,  in  some  high  ratio,  proportionate  to  its  elevation  of 
temperature.  If  several  concentric  circular  wicks,  or  several 
parallel  flat  wicks,  be  burnt  near  together,  they  produce  more 
light,  in  consequence  of  the  accumulation  of  heat,  than  they 
would  do,  if  burnt  separately. 

Glass  Shades. — To  relieve  the  eye  from  the  glare  of  light, 
produced  by  bright  lamps,  shades  of  roughened  glass  are  fre- 
quently used.  A  rough  surface  upon  glass  may  be  produced 
by  grinding  it  with  sand  or  emery,  by  corroding  it  with  fluoric 
acid,  or  by  covering  it  with  powdered  glass  and  exposing  it  to 
heat,  till  the  particles  adhere.  Glass  shades  have  the  effect  to 
disperse  the  rays  of  light,  by  the  numerous  reflections  and  re- 
fractions which  they  occasion ;  till  at  length  the  light  issues  from 
all  parts  of  their  surface,  and  it  appears  as  if  the  glass  itself 
were  the  luminous  body. 

Sinumbral  Lamp. — The  reservoir  of  the  sinumbral  lamp,  is 
constructed  on  the  same  general  principles  with  that  of  the  As- 
tral. The  ring,  however,  which  holds  the  oil,  is  so  formed  as 
to  oppose  the  smallest  diameter  of  its  section  to  the  rays  of 
light.  A  large  shade  of  ground  glass  is  used,  which  nearly  in- 
closes the  light,  and  by  the  different  refractions  and  reflections 
given  to  the  rays  by  the  ground  glass,  they  escape  in  all  direc- 
tions, so  that  there  is  no  perceptible  shadow  at  a  small  distance 
from  the  ring.  Reflectors  are  sometimes  added,  when  it  is  de- 
sired to  throw  the  principal  mass  of  light  in  one  direction. 

Measurement  of  Light. — The  following  method  of  measur- 
ing the  comparative  illuminating  power  of  different  lights,  is 
founded  on  the  law,  that  the  amount  of  rays  thrown  on  a  given 
surface,  is  inversely  as  the  square  of  the  distance  of  the  illumi- 


184 


ARTS   OF  ILLUMINATION. 


nating  body.  Place  two  lights,  which  are  to  be  compared  with 
each  other,  at  the  distance  of  a  few  feet,  or  yards,  from  a  screen 
of  white  paper,  or  a  white  wall.  On  holding  a  small  card 
near  the  wall,  two  shadows  will  be  projected  on  it,  the  darker 
one  by  the  interception  of  the  brighter  light,  and  the  fainter 
shadow  by  the  interception  of  the  duller  light.  Bring  the  faint- 
•er  light  nearer  to  the  card,  or  remove  the  brighter  light  farther 
from  it,  till  both  shadows  acquire  the  same  intensity,  which  the 
eye  can  judge  of  with  great  precision,  particularly  from  the 
conterminous  shadows  at  the  angles.  Measure  now  the  distan- 
ces of  the  two  lights  from  the  wall  or  screen,  and  the  squares 
of  these  distances  will  give  the  ratio  of  illumination.  Thus  if 
an  Argand  flame  and  a  candle  stand  at  the  distances  of  ten  feet 
and  four  feet  respectively,  when  their  shadows  are  equally  deep 
we  have  the  square  of  ten  and  the  square  of  four,  or  100  and 
16,  as  their  relative  quantities  of  light.  In  this  experiment  the 
spectator  should  be  equidistant  from  each  shadow. 

Gas  Lights. — In  the  flame  of  a  common  lamp  or  candle, 
the  combustible  matter  is  not  burnt  until  it  has  first  been  con- 
verted into  vapor,  or  inflammable  gas.  This  gaseous  matter  is 
burnt  as  fast  as  it  is  generated,  in  consequence  of  being  brought 
immediately  in  Contact  with  the  atmospheric  air,  and  set  on  fire 
by  the  same  heat  which  produces  it.  It  is  found,  however,  if 
certain  combustibles  be  exposed  to  heat,  and  if  the  inflamma- 
ble gas,  w^hich  they  yield,  be  kept  separate  from  the  atmospher- 
ic air,  that  this  gas  may  be  conveyed  in  pipes  to  any  distance, 
and  burnt  for  light  in  any  place  where  a  stream  of  it  is  discharg- 
ed into  the  atmosphere.  In  this  way  various  combustibles  may 
be  used  which  are  not  capable  of  being  burnt  in  lamps,  and  a 
brilliant  and  economical  light  obtained  from  them.  The  ma- 
terials chiefly  employed  for  this  purpose,  are  pitcoal,  and  ani- 
mal oil.  Various  other  substances  are  capable  of  support- 
ing gas  lights,  such  as  bitumen,  rosin,  oleaginous  vegetable 
seeds,*  other  oily  or  resinous  bodies,  and  even  wood,  and  turf. 

*  Professor  Olmstead  has  found  that  cotton  seed  produces  gas  of  a  superior 
kind  for  purposes  of  illumination.  See  his  account  of  this  article  in  Silliman's 
Journal,  vol.  viii.  p.  294,  and  x,  363. 


ARTS   OF  ILLUMINATION. 


185 


The  inflammable  gas.  which  is  procured  from  all  these  substan- 
ces is  chiefly  carburetted  hydrogen.  Of  this  two  kinds  are 
known,  the  first  sometimes  called  olefiant  gas,  and  the  other  sub- 
carburetted  hydrogen.  Mr  Brande,  however,  considers  the 
last  species  as  merely  a  mixture  of  the  first,  with  hydrogen. 
The  fitness  of  a  mixed  gas  for  purposes  of  illumination,  is  de- 
pendant on  the  quantity  of  carburetted  hydrogen  which  it  con- 
tains, other  things  being  equal. 

Coal  Gas. — The  use  of  coal  gas  for  purposes  of  illumina- 
tion, appears  to  have  been  first  introduced  by  Mr  Murdoch,  in 
1792,  although  its  power  of  affording  a  luminous  flame  was 
known  much  earlier.  It  is  found  that  the  bituminous  coals, 
and  particularly  cannel  coal,  afford  the  most  and  the  best  illu- 
minating gas.  Some  of  the  Anthracites,  according  to  Profes- 
sor Silliman,  afford  as  much  gas  as  Liverpool  coal,  but  it  burns 
with  a  feeble  flame,  and  is  unfit  for  the  purposes  of  illumina- 
tion. 

In  the  manufacture  of  coal  gas,  the  coal  is  placed  in  iron 
retorts,  which  are  subjected  to  a  strong  heat  in  a  furnace.  The 
gas  is  thus  driven  off  mixed  with  the  vapor  of  tar,  oil,  and  am- 
moniacal  water,  and  in  this  state  is  conducted  by  pipes  first  in- 
to a  horizontal  trunk  of  cast  iron,  called  the  hydraulic  main, 
and  from  thence  into  a  condensing  apparatus,  surrounded  with 
cold  water,  where  the  vapors  of  the  tar,  oil,  and  water,  are 
condensed  and  fall  down,  while  the  gaseous  product  is  convey- 
ed along,  containing  several  impure  gases,  such  as  sulphuretted 
hydrogen,  and  carbonic  acid. 

In  order  to  separate  the  carburetted  hydrogen,  from  these 
impurities,  various  contrivances  have  been  adopted.  The  usual 
method  of  purifying  coal  gas,  is  to  make  it  pass  through  a  mix- 
ture of  lime  and  water  called  Cream  of  Lime,  which  absorbs  or 
combines  with  the  contaminating  gases.  For  this  purpose  a 
considerable  number  of  purifiers  are  erected,  and  the  lime  and 
water  are  kept  in  a  state  of  constant  agitation,  either  by  a  steam 
engine,  or  by  one  or  two  men,  till  the  gas  is  rendered  sufficient- 
ly pure.  Sometimes  the  purification  is  effected  by  causing  the 
24 


186 


ARTS   OF  ILLUMINATION. 


gas  to  pass  in  contact  with  solid  lime,  newly  slaked ;  and  some- 
times by  passing  it  through  retorts  containing  clippings  of  iron 
made  red  hot.  When  thus  purified  the  gas  is  conveyed  by  a 
pipe  to  the  gasometer. 

The  Gasometer,  is  a  large  inverted  vessel,  made  of  mallea- 
ble iron,  or  copper,  either  of  a  cylindrical  or  rectangular  form, 
and  suspended  over  a  reservoir  of  water  of  a  Ihtle  larger  size,  by 
means  of  counter-weights.  The  gas  is  introduced  by  pipes 
ascending  from  the  bottom  of  the  reservoir,  and  rising  a  little 
above  the  surface  of  the  water.  While  the  gasometer  is  filling 
with  gas,  it  gradually  rises  out  of  the  water,  until  it  is  filled,  af- 
ter which  no  more  gas  is  admitted,  and  its  contents  are  ready 
to  be  distributed  through  the  pipes  by  which  it  is  to  be  convey- 
ed to  the  place  intended  to  be  illuminated  by  burning  it.  As 
the  gas  is  forced  out  by  the  weight  of  the  gasometer,  and  is 
burned,  the  gasometer  descends  gradually  in  the  water,  till  the 
whole  of  its  contents  are  expelled,  when  it  is  again  filled  by 
the  same  process  as  before. 

The  gas  being  thus  ready  for  use,  must  be  carried  off  by 
pipes,  the  diameter  of  which  is  proportional  to  the  degree  of 
light  required.  It  has  been  found  that  a  pipe  one  inch  in  diam- 
eter, will,  under  a  pressure  of  a  column  of  water  from  five 
eights  to  three  fourths  of  an  inch,  supply  gas  equal  to  100  can- 
dles ;  and  if  there  was  no  friction,  or  mechanical  impediment, 
the  number  of  candles  would  be  found  for  other  diameters  of 
pipe,  by  multiplying  the  square  of  the  diameter  of  the  pipe  in 
inches  by  100.  The  friction,  however,  or  obstruction,  dimin- 
ishes so  rapidly  with  the  diameter  of  the  pipe,  that  the  number 
of  candles  is  always  greater  than  this  rule  gives.  Thus  a  pipe 
three  inches  in  diameter  will  supply  light  equal  to  1000  candles — 
a  pipe  four  inches,  2000 — a  pipe  six  inches,  5000 — and  a  pipe 
ten  inches,  about  14,000."^ 

When  the  gas  is  to  be  burned  in  rooms,  shops,  or  streets,  it 
is  allowed  to  escape  through  small  circular  apertures  of  from 


*  Brewster's  Edition  of  Ferguson's  Mechanics,  vol.  ii.  p.  273. 


ARTS  OF  ILLUMINATION. 


187 


on<3  fortieth  to  one  sixtieth  of  an  inch  in  diameter,  which  may- 
be arranged  in  various  ornamented  ways,  or  disposed  in  a  cir- 
cle, like  an  argand  burner,  with  a  current  of  air  running  be- 
tween them.  The  lights  thus  produced  are  equal,  steady,  and 
of  the  most  brilliant  kind.  When  the  supply  of  gas  is  cut  off, 
they  are  instantly  extinguished.  When  it  is  restored,  the  invisi- 
ble current  flows  out,  and  may  be  instantly  lighted  again  by  the 
contact  of  flame. 

Oil  Gas. — It  has  been  long  known  to  chemists,  that  wax, 
-oil,  tallow,  he,  when  passed  through  ignited  tubes,  are  resolved 
into  combustible  gaseous  matter,  which  burns  with  a  bright  light. 
Of  late  years  this  gas  has  been  much  used  for  purposes  of  illu- 
mination. Oil  gas  is  considered  in  many  respects  superior  to 
coal  gas,  and  free  from  its  inconveniences.  The  material  from 
which  it  is  produced  containing  no  sulphur  or  other  matter  by 
which  coal  gas  is  contaminated,  it  never  produces  a  suffocating 
smell  in  rooms;  so  that  the  costly  operation  of  purifying  the 
gas  by  lime,  and  other  means,  is  avoided.  Nothing  is  con- 
tained in  oil  gas  which  can  injure  the  metal  of  which  the  con- 
veyance pipes  are  made. 

The  oil  gas  has  a  further  advantage  over  coal  gas,  in  con- 
taining a  greater  proportion  of  carburetted  hydrogen,  so  that 
one  cubic  foot  of  oil  gas  is  said  to  go  as  far  as  two  or  three  of 
coal  gas.  This  circumstance  is  of  importance,  as  it  reduces  in 
the  same  proportion,  the  size  of  the  gasometers,  which  are  ne- 
cessary to  contain  it.  Oil  gas  contains  about  75  per  cent,  of 
carburetted  hydrogen,  while  purified  coal  gas  but  seldom  con- 
tains more  than  40  per  cent. 

In  procuring  this  gas  a  quantity  of  oil  is  placed  in  an  air-tight 
vessel,  in  such  a  manner,  that  it  may  pass  slowly  into  retorts  or 
iron  tubes,  which  are  kept  at  a  moderate  red  heat.  Fragments 
of  coke  or  brick,  are  usually  inclosed  in  the  tubes.  The 
oil,  in  its  passage  through  the  retorts,  is  principally  decomposed, 
and  converted  into  gas  proper  for  illumination,  carrying  with  it, 
however,  some  oil  in  the  state  of  vapor.  To  purify  the  gas 
from  this  oil,  which  is  suspended  in  it,  and  which  occasions  an 


188 


ARTS  OF  ILLUMINATION. 


empyreumatic  smell,  it  is  conveyed  into  wash  vessels,  where, 
by  bubbling  through  water,  or  through  fresh  oil,  it  is  cooled  and 
rendered  fit  for  use.  It.  then  passes  by  a  proper  pipe  into  a 
gasometer,  from  which  it  is  suffered  to  pass  off  in  pipes,  in  the 
usual  manner,  to  its  places  of  destination. 

The  poorest  kinds  of  oil,  which  are  unfit  for  burning  in  lamps, 
produce  excellent  gas.  This  is,  indeed,  the  chief  source  of 
economy  in  the  process. 

According  to  Mr  Brande,  a  light  equal  to  ten  wax  candles 
for  one  hour,  requires  for  its  production,  2600  cubic  inches  of 
pure  carburetted  hydrogen,  or  olefiant  gas,  4875  cubic  inches 
of  oil  gas,  or  13120  cubic  inches  of  coal  gas. 

Gasmeter. — In  dispensing  gas  for  the  illumination  of  partic- 
ular rooms,  it  was  found  necessary  to  possess  some  method  of 
measuring  the  quantity  expended  in  each  place.  An  ingenious 
instrument  called  the  gasmeter  has  been  introduced  for  this 
purpose.  It  consists  of  a  horizontal  cylinder  partly  filled  with 
water,  within  which  another  cylinder  revolves  on  an  axis,  hav- 
ing its  interior  surface  divided  into  several  compartments. 
These  compartments,  being  successively  filled  with  the  gas,  as 
it  passes  through,  rise  out  of  water  like  inverted  buckets  of  an 
overshot  wheel,  and  cause  the  inner  cyhnder  to  revolve.  The 
number  of  revolutions  is  registered  by  machinery,  and  thus  the 
quantity  of  gas  which  escapes  in  a  given  time  is  estimated. 

Portable  Gas  Lights. — The  magnitude  and  expense  of  gas 
works,  prevents  the  use  of  them,  except  in  cases  where  a  large 
number  of  lights  are  wanted,  within  a  convenient  distance  from 
the  gasometer.  The  gas,  however,  may  be  conveyed  to  any 
distance,  by  condensing  it  in  strong  vessels  of  iron  or  copper, 
made  of  a  small  or  portable  size.  The  gas  is  forced  into  these 
vessels  by  a  condensing  pump,  and  when  afterwards  suffered  to 
escape  through  a  small  orifice,  is  capable  of  supporting  a  flame 
for  many  hours.  The  economy,  however,  of  this  process  has 
been  doubted. 

Safety  Lamp. — In  coal  mines  an  inflammable  gas  is  generat- 
ed, called  Jire  damp  by  the  miners,  and  composed  chiefly  of 


ARTS   OF  ILLUMINATION. 


189 


carburetted  hydrogen.  This  gas  when  mixed  with  atmospheric 
air  is  liable  to  take  fire  from  the  flame  of  a  lamp  or  candle, 
and  to  explode  with  great  violence.  Terrible  accidents  have 
happened,  and  many  lives  have  been  destroyed,  from  these  ex- 
plosions. To  prevent  such  accidents,  several  troublesome  and 
circuitous  modes  of  obtaining  light  were  resorted  to  by  the  mi- 
ners; such  as  striking  sparks  from  a  wheel,  and  inclosing  a 
lamp  within  a  tight  lantern,  which  was  supplied  with  air  from  a 
bellows.  All  these  are  now  superseded  by  the  safety  lamp  of 
Sir  Humphrey  Davy.  This  important  invention  consists  simply 
of  a  lamp,  the  flame  of  which  is  wholly  enclosed  in  a  cylinder 
of  fine  wire  gauze.  Its  operation  depends  on  the  principle 
discovered  by  Sir  H.  Davy,  that  explosive  mixtures  cannot  be 
inflamed  through  minute  apertures  in  metallic  surfaces,  or  tis- 
sues. The  wire  gauze,  being  a  powerful  conductor  and  radia- 
tor of  heat,  cools  a  flame  which  is  in  contact  w^ith  it,  so  as  to 
deprive  it  of  the  power  of  producing  an  explosion  on  the  other 
side.  If  this  lamp  be  immersed  in  an  explosive  mixture,  the 
gas  will  be  inflamed,  and  burn  on  the  inside  of  the  gauze  cy- 
linder, but  not  on  the  outside.  In  these  cases  the  flame  of  the 
lamp  first  enlarges,  and  is  then  extinguished,  the  whole  of  the 
cage  being  filled  with  a  lambent  blue  light.  If  the  supply  of 
gas  be  withdrawn,  this  appearance  gradually  ceases,  and  the 
wick  becomes  rekindled. 

Lamp  without  Flame. — This  curious  instrument  may  be 
made  by  winding  upon  the  wick  of  a  lamp  containing  alcohol, 
a  fine  wire  of  platinum,  not  more  than  a  hundredth  part  of  an 
inch  in  thickness.  There  should  be  about  sixteen  spiral  turns, 
one  half  of  which  should  surround  the  wick,  and  the  other  half 
rise  above  it.  Having  lighted  the  lamp  for  an  instant,  on  blow- 
ing it  out,  the  wire  will  become  brightly  ignited,  and  will  con- 
tinue to  glow  as  long  as  any  alcohol  remains,  without  the  blaze 
being  any  more  renewed.  The  principle  depends  upon  the 
slow  combustion  which  is  found  to  take  place  in  inflammable  or 
explosive  mixtures,  at  a  lower  temperature  than  is  necessary  to 
produce  inflammation.    This  combustion  is  not  visible,  but  the 


190 


ARTS  OF  ILLUMINATION. 


heat  is  nevertheless  sufficient  to  ignite  minute  solids  exposed  to 
its  influence.  In  the  lamp  which  has  been  described,  the  ex- 
plosive mixture  is  the  vapor  of  alcohol  and  atmospheric  air. 
But  the  experiment  may  be  varied,  by  using  ether,  camphor, 
&ic.,  and  by  substituting  platinum  leaf  for  wire. 

Modes  of  procuring  Light. — To  obtain  light  and  fire,  when 
wanted,  in  an  expeditious  manner,  various  instruments  have  been 
introduced,  constructed  on  optical,  mechanical,  and  chemical 
principles.  The  methods  by  which  they  operate  are  chiefly 
the  following.  1.  By  concentration  of  the  solar  rays,  as  in  the 
focus  of  a  common  lens,  or  burning  glass.  2.  By  friction. 
Dry  wood  takes  fire,  if  rubbed  violently  in  the  manner  practis- 
ed by  savages,  or  if  it  be  held  against  the  surface  of  a  wheel 
which  revolves  rapidly.  Phosphorus  takes  fire  by  very  slight 
friction,  and  on  this  account  is  used  in  the  phosphoric  fire  hot- 
ties,  the  matches  of  which,  after  being  charged  with  a  minute 
quantity  of  phosphorus,  take  fire  by  rubbing  them  on  the  cork. 
3.  By  percussion.  When  hard  bodies,  such  as  flint  and  steel, 
are  brought  into  collision,  small  particles  of  ignited  matter  are 
struck  off  in  the  form  of  sparks,  which  are  sufficiently  hot  to 
set  fire  to  tinder,  gunpowder,  &:c.  Common  firelocks,  tinder 
boxes,  Sic,  operate  on  this  principle.  4.  By  Compression.  If 
a  piece  of  tinder  is  confined  in  a  small  cavity  at  the  end  of  a 
condensing  syringe,  it  will  take  fire,  if  the  piston  of  the  syringe 
be  driven  down  with  a  stroke,  so  as  suddenly  to  condense  the 
air.  The  tinder  commonly  used  for  this  purpose,  is  what  is 
called  German  tinder,  made  of  a  fungus  that  grows  on  trees, 
{^Boletus  igniarius)  boiled  in  a  solution  of  nitre  and  dried.  5. 
By  chemical  action.  In  the  oxymuriatic  fire  hoxes,\he  match- 
es are  charged  with  chlorate  of  potash  mixed  with  sulphur  or 
some  other  combustible.  When  these  are  brought  into  contact 
with  sulphuric  acid,  a  violent  chemical  action  takes  place,  and 
the  match  takes  fire.  Yiomher^s  pyrophor us  takes  fire  on  ex- 
posure to  the  air.  It  may  be  made  by  calcining  alum  with  less 
than  an  equal  quantity  of  flour  or  sugar,  until  the  smoke  and 
flame  disappear.    It  is  then  kept  in  close  stopped  bottles,  and 


ARTS  OF  ILLUMINATION. 


191 


if  a  little  of  it  be  shaken  out  upon  any  light  combustible,  as  cot- 
ton or  tow,  it  causes  it  to  inflame.  The  platinum  lights  de- 
pend on  a  remarkable  property  discovered  by  Dobereiner,  in 
platinum,  by  which  a  sponge  made  of  that  metal,  becomes  ig- 
nited when  exposed  to  a  stream  of  hydrogen  gas. 


AccuM,  on  Gas-light,  8vo.  1816; — Peckston,  on  Gas-lighting; — 
Rumford's  Works; — Nicholson's  Philosophical  Journal,  vol.  i.  4to. 
vol.  xiv.  8vo.  &c. ; — Rees's  Cyclopedia; — Ure's  Chemical  Dictionary. 


CHAPTER  X. 


ARTS  OF  LOCOMOTION. 

Animals  of  the  more  perfect  kinds,  possess  the  power  of  shift- 
ing their  place  at  will,  which  power  they  exercise  both  in  trans- 
porting their  own  bodies  and  in  conveying  other  masses  of  mat- 
ter. The  chief  obstacles  which  oppose  locomotion,  or  change 
of  place,  are  gravity  and  friction,  the  last  of  which  is  in  most 
cases  a  consequence  of  the  first.  Gravity  confines  all  terres- 
trial bodies  against  the  surface  of  the  earth,  with  a  force  pro- 
portionate to  the  quantity  of  matter  which  composes  them. 
Before  they  can  be  removed  from  one  spot  of  this  surface  to  anoth- 
er of  equal  height,  they  must  either  be  lifted  from  the  ground 
against  the  force  of  gravity,  or  carried  horizontally  along  the 
surface,  resisting  with  a  degree  of  friction,  which  increases  with 
their  weight.  Most  kinds  of  mechanism,  both  natural  and  ar- 
tificial, which  assist  locomotion,  are  arrangements  for  obviating 
the  effects  of  gravity  and  friction. 

Motion  of  Animals. — Animals  that  walk,  obviate  friction  by 
substituting  points  of  their  bodies  instead  of  large  surfaces,  and 
upon  these  points  they  turn,  as  upon  centres,  for  the  length  of 
each  step,  raising  themselves  wholly  or  partly  from  the  ground 
in  successive  arcs,  instead  of  drawing  themselves  along  the  sur- 
face. The  line  of  arcs  which  the  centre  of  gravity  describes, 
is  converted  into  an  easy  or  undulating  line,  by  the  compound 
action  of  the  different  joints.  As  the  feet  move  in  separate 
lines,  the  body  has  also  a  lateral,  vibratory  motion.  A  man, 
in  walking,  puts  down  one  foot  before  the  other  is  raised,  but 
not  in  running.  Quadrupeds  in  walking  have  three  feet  upon 
the  ground  for  most  of  the  time ;  in  trotting,  only  two.  Animals 
which  walk  against  gravity,  as  the  common  fly,  the  tree  toad,  Sic, 


ARTS  OF  LOCOMOTION. 


198 


support  themselves  by  suction,  using  cavities  on  the  under  side 
of  their  feet,  which  they  enlarge  at  pleasure,  till  the  pressure 
of  the  atmosphere  causes  them  to  adhere.  In  other  respects 
their  locomotion  is  effected  like  that  of  other  walking  animals. 
Birds  perform  the  motion  of  flying  by  striking  the  air  with  the 
broad  surface  of  their  wings  in  a  downward  and  backward 
direction,  thus  propelling  the  body  upward  and  forward.  Af- 
ter each  stroke  the  wings  are  contracted,  or  slightly  turned,  to 
lessen  their  resistance  to  the  atmosphere,  then  raised  and 
spread  anew.  The  downward  stroke  also,  being  more  sudden 
than  the  upward,  is  more  resisted  by  the  atmosphere.  The 
tail  of  birds  serves  as  a  rudder  to  direct  the  course  upward  or 
downward.  When  a  bird  sails  in  the  air  without  moving  the 
wings,  it  is  done  in  some  cases  by  the  velocity  previously  ac- 
quired, and  an  oblique  direction  of  the  wings  upward  ; — in 
others,  by  a  gradual  descent,  with  the  wings  slightly  turned  in 
an  oblique  direction  downward.  Fishes,  in  swimming  for- 
ward, are  ])ropelled  chiefly  by  strokes  of  the  tail,  the  extremity 
of  which  being  bent  into  an  oblique  position,  propels  the  body 
forward  and  laterally  at  the  same  time.  The  lateral  motion  is 
corrected  by  the  next  stroke,  in  the  opposite  direction,  while 
the  forward  course  continues.  The  fins  serve  partly  to  assist 
in  swimming,  but  chiefly  to  balance  the  body,  or  keep  it  up- 
right ;  for  the  centre  of  gravity  being  nearest  the  back,  a  fish 
turns  over,  when  it  is  dead,  or  disabled.*  Some  other  aquatic 
animals,  as  leeches,  swim  with  a  sinuous  or  undulating  motion 
of  the  body,  in  which  several  parts  at  once  are  made  to  act  ob- 
liquely against  the  water.  Serpents  in  like  manner  advance 
by  means  of  the  winding  or  serpentine  direction  which  they 
give  to  their  bodies,  and  by  which  a  succession  of  oblique  for- 
ces are  brought  to  act  against  the  ground.  Sir  Everard  Home 
is  of  opinion  that  serpents  use  their  ribs  in  the  manner  of  legs, 

*  The  swimming  bladder  which  exists  in  most  fishes,  though  not  in  all,  is 
supposed  to  have  an  agency  in  adapting  the  specific  gravity  of  the  fish  to  the 
particular  depth  in  which  it  resides.    The  power  of  the  animal  to  rise  or  sink 
by  altering  the  dimensions  of  this  organ,  has  been,  with  some  reason,  disputed. 
25 


194 


ARTS  OF  LOCOMOTION. 


and  propel  the  body  forwards  by  bringing  the  plates  on  the  un- 
der surface  of  the  body  to  act  successively  like  feet  against  the 
ground.  ^  Some  worms  and  larva?  of  slow  motion,  extend  a 
part  of  their  body  forwards,  and  draw  up  the  rest  to  overtake  it, 
some  performing  this  motion  in  a  direct  line,  others  in  curves. 

When  land  animals  swim  in  water,  they  are  supported, 
because  their  whole  weight,  with  the  lungs  expanded  with  air, 
is  less  than  that  of  an  equal  bulk  of  water.  The  head,  howev- 
er, or  a  part  of  it,  must  be  kept  above  water  to  enable  the  ani- 
mal to  breathe,  and  to  effect  this  and  also  to  make  progress  in 
the  water,  the  hmbs  are  exerted  in  successive  impulses  against 
the  fluid.  Quadrupeds  and  birds  swim  with  less  effort  than 
man,  because  the  weight  of  the  head,  which  is  carried  above 
water,  is,  in  them,  a  smaller  proportional  part  of  the  whole, 
than  it  is  in  man. 

Inertia. — In  consequence  of  the  action  of  gravity  upon  bod- 
ies, their  inertia  becomes  a  greater  obstacle  to  locomotion  than 
it  would  otherwise  be.  Every  body  tends  by  its  inertia  to 
preserve  a  state  of  rest,  if  it  is  still,  and  of  uniform  rectilinear 
motion,  if  it  is  not  still.  Changes,  therefore,  not  only  from  rest 
to  motion,  but  also  changes  of  direction  and  changes  of  speed, 
are  resisted  by  the  force  of  inertia.  Bodies  moving  upon  the 
earth's  surface  are  obliged  by  their  gravity  to  accommodate 
their  motions  to  the  irregularities  of  this  surface,  and  conse- 
quently to  change  often  both  their  direction  and  velocity.  The 
inertia  thus  becomes  a  continual  source  of  expenditure  of  pow- 
er, although  it  would  not  be  so,  if  bodies  moved  at  a  uniform 
rate  and  in  a  straight  course. 

Aids  to  Locomotion. — All  animals  are  provided  by  nature 
with  organs  of  locomotion  best  adapted  to  their  structure  and 
situation,  and  it  is  probable  that  no  animal,  man  not  being  ex- 

*  Lectures  on  Comparative  Anatomy,  vol.  i.  p.  116,  &c.  Sir  E.  Home  de- 
duces this  fact  from  tlie  anatomy  of  the  animal,  and  from  the  movements 
which  he  perceived,  in  suffering  a  large  coluber  to  cravi^l  over  his  hand.  The 
ribs  appeared  to  be  raised,  spread,  carried  forward,  depressed  and  pushed 
backward,  successively. 


ARTS  OF  LOCOMOTrON. 


195 


cepted,  can  exert  his  strength  more  advantageously  by  any  oili- 
er tlian  the  natural  mode,  in  moving  himself  over  the  common 
surface  of  the  ground.  *  Thus  walking  cars,  velocipedes,  he, 
although  they  may  enable  a  man  to  increase  his  velocity  in  fa- 
vorable situations  for  a  short  time,  yet  they  actually  require  an 
increased  expenditure  of  power,  for  the  purpose  of  transporting 
the  machine  made  use  of,  in  addition  to  the  weight  of  the 
body.  When,  however,  a  great  additional  load  is  to  be  trans- 
ported with  the  body,  a  man,  or  animal,  may  derive  much  assist- 
ance from  mechanical  arrangements. 

Wheel  Carriages. — For  moving  weights  over  the  common 
ground  with  its  ordinary  asperities  and  inequalities  of  substance 
and  structure,  no  piece  of  inert  mechanism  is  so  favorably 
adapted  as  the  wheel  carriage.  It  was  introduced  into  use  in  very 
early  ages,  as  affording  a  facility  for  the  carrying  of  heavy  loads, 
and  finally  for  transporting  man  himself ;  not  by  his  own  pow- 
ers, but  by  the  strength  of  other  animals  which  he  had  subjugat- 
ed to  his  use.  Chariots  were  used  in  war,  and  waggons  in 
agriculture,  at  a  very  remote  period. 

Wheels. — The  mechanical  action  of  wheels  applied  to  loco- 
motive carriages  is  twofold.  They  diminish  friction,  and  also 
surmount  obstacles  or  inequalities  of  the  road,  with  more  ad- 
vantage than  bodies  of  any  other  form,  in  their  place,  could  do. 
The  friction  is  diminished  by  transferring  it  from  the  surface  of 
the  ground  to  the  centre  of  the  wheel,  or  rather  to  the  place  of 
contact  between  the  axletree  and  the  box  of  the  wheel.  So 
that  it  is  lessened  by  the  mechanical  advantage  of  the  lever,  in 
the  proportion  which  the  diameter  of  the  axletree  bears  to  the 
diameter  of  the  wheel.  The  rubbing  surfaces  also,  being  kept 
polished  and  smeared  with  some  unctuous  substance,  are  in  the 
best  possible  condition  to  resist  friction. 

In  like  manner  the  common  obstacles  that  present  themselves 
in  the  public  roads,  are  surmounted  by  a  wheel  with  peculiar 

*  This  remark  of  course  does  not  apply  to  situations  in  v/liich  friction  is  ob- 
viated, as  upon  water,  ice,  rail  roads,  &c. 


196 


ARTS  OF  LOCOMOTION. 


facility.  As  soon  as  the  wheel  strikes  against  a  stone  or  simi- 
lar bard  body,  it  is  converted  into  a  lever  for  lifting  the  load 
over  the  resisting  object.  If  an  obstacle  eight  or  ten  inches  in 
height  were  presented  to  the  body  of  a  carriage  unprovided 
with  wheels,  it  woiild  stop  its  progress,  or  subject  it  to  such  vio- 
lence as  would  endanger  its  safety.  But  by  the  action  of  a 
wheel,  the  load  is  lifted,  and  its  centre  of  gravity  passes  over  in 
the  direction  of  an  easy  arc,  the  obstacle  furnishing  the  fulcrum 
on  which  the  lever  acts. 

Rollers. — Rollers  placed  under  a  heavy  body  diminish  the 
friction  in  a  greater  degree  than  wheels,  provided  they  are  true 
spheres  or  cylinders,  without  any  axis  on  which  they  are  con- 
strained to  move.  If  the  rollers  be  perfectly  elastic  and  also 
the  plane  upon  which  they  move,  there  will  be  no  sliding  fric- 
tion whatever ;  whereas  the  wheel  always  rubs  at  its  axis.  But 
an  offset  for  this  advantage  is  found  in  the  circumstance,  that 
the  wheel  maintains  its  relative  place  in  regard  to  the  load, 
while  the  roller  constantly  falls  behind,  and  is  obliged  to  be 
taken  up  and  replaced,  at  an  expense  of  power.  A  cylindrical 
roller  likewise  occasions  friction,  whenever  its  path  deviates 
in  the  least  from  a  straight  line. 

Size  of  Wheels.— ^he  mechanical  advantages  of  a  wheel 
are  proportionate  to  its  size,  and  the  larger  it  is,  the  more 
effectually  does  it  diminish  the  ordinary  resistances.  A  large 
wheel  will  surmount  stones  and  similar  obstacles  better  than  a 
small  one,  since  the  arm  of  the  lever  on  which  the  force  acts  is 
longer,  and  the  curve  described  by  the  centre  of  the  load  is  the 
arc  of  a  larger  circle,  and  of  course  the  ascent  is  more  gradual 
and  easy,  ^ 

A  further  advantage  is  derived  from  the  circumstance,  that  in 
passing  over  holes,  ruts,  or  excavations,  a  large  wheel  sinks  less 
than  a  small  one,  and  consequently  occasions  less  jolting  and 

*  If  the  plane  on  which  a  carriage  moves,  and  the  line  of  draught  be  both 
horizontal,  the  advantage  for  surmounting  an  immoveable  obstacle  of  a  given 
height,  is  as  the  square  root  of  the  radius  of  the  wheel. — See  Playfaifs 
Outlines  of  JVatural  Philosophy,  vol  i.  p.  103. 


ARTS  OP  LOCOMOTION. 


197 


expenditure  of  power.  The  wear  also  of  small  wheels  ex- 
ceeds that  of  larger  ones,  for  if  we  suppose  a  wheel  to  be  three 
feet  in  diameter,  it  will  turn  round  twice,  while  a  wheel  six  feet 
in  diameter  turns  round  once.  Of  course  its  tire  will  come 
twice  as  often  in  contact  with  the  ground,  and  its  spokes  will 
twice  as  often  have  to  support  the  weight  of  the  load.  So  that 
by  calculation,  it  should  last  but  half  the  length  of  time. 

On  these  accounts  it  would  be  advantageous  to  augment  the 
diameter  of  wheels  to  a  great  extent,  were  it  not  for  certain 
practical  limits  which  it  is  not  found  useful  to  exceed.  One 
of  these  is  found  in  the  nature  al  the  materials  which  we  are 
obliged  to  use,  and  which,  if  employed  to  make  wheels  of  great 
size,  at  the  same  time  preserving  the  requisite  strength,  would 
render  them  cumbersome  and  too  heavy  for  use.  Another 
reason  for  regulating  the  size  of  wheels  by  a  hmited  standard 
arises  from  the  relative  size  of  the  animals  commonly  employed 
for  draught.  A  wheel  should  seldom  be  of  such  dimensions 
that  its  centre  would  exceed  in  height  the  breast  of  the  horse, 
or  other  animal,  by  which  it  is  drawn ;  because  if  this  were 
the  case,  the  horse  would  draw  obhquely  downward,  as  well  as 
forward,  and  expend  a  part  of  his  strength  in  acting  against  the 
ground. 

Ldne  of  Traction, — In  practice  it  is  even  found  necessary  to 
place  the  point  of  draught  or  centre  of  the  wheels  lower  than 
the  middle  of  the  horse's  breast,  for  various  reasons.  1.  The 
shape  of  the  animal's  shoulders  require  this  direction.  2.  The 
horse  exerts  a  greater  force  in  proportion  as  the  line  of  draught 
passes  near  the  fulcrum,  which  is  in  his  hind  feet.  3.  If  a 
horse  draws  obliquely  upward,  a  part  of  his  force  is  employed 
in  lessening  the  pressure  on  the  ground,  and  to  answer  this 
purpose  most  effectually,  it  has  been  remarked  that  the  inchna- 
tion  of  the  traces,  or  shafts,  ought  to  be  the  same  with  that  of  a 
road,  upon  which  the  carriage  would  just  descend  by  its  own 
weight,  f    According  to  Dr  Gregory,  a  power  which  moves  a 

*  See  the  article  Limit  of  Bulk,  p.  48. 

t  Young's  Natural  Philosophy,  vol.  i.  p.  216. 


1D8 


ARTS  or  LOCOMOTION. 


sliding  body  along  a  horizontal  plane,  acts  with  the  greatest  ad- 
vantage as  far  as  friction  is  concerned,  when  the  line  of  direc- 
tion makes  an  angle  of  about  18^  degrees  with  the  plane. 
M.  Deparcieux  states  from  experiments  with  carriages,  that  the 
angle  made  by  the  trace  with  a  horizontal  line,  should  be  one  of  14 
or  15  degrees.  4.  Another  reason  for  inclining  the  line  of 
draught,  is,  that  a  horse  depresses  his  body  in  proportion  to  the 
force  he  is  obliged  to  exert,  in  order  that  he  may  bring  his  own 
weight  to  act  more  advantageously  upon  the  load.  M.  Deparcieux 
has  demonstrated  that  animals  draw  through  the  medium  of 
their  weight,  in  all  our  commoii  •  vehicles ;  and  this  fact  becomes 
obvious  when  we  consider,  that  if  a  horse  had  no  weight,  he 
would  be  unable  to  draw,  but  would  simply  be  raised  on  his 
hind  feet,  by  any  exertion  to  advance  while  in  his  harness. 

In  the  foregoing  considerations,  it  is  necessary  to  recollect 
that  the  conditions  which  enable  a  horse  to  exert  his  greatest 
force,  are  not  those  w^hich  promote  his  greatest  velocity,  and 
that  the  means  of  increasing  his  speed,  are  obtained,  as  in  other 
cases,  by  the  sacrifice  of  power. 

When  there  are  four  wheels,  the  line  of  draught  ought  to  be 
directed  to  a  point  between  the  two  axletrees,  or  rather  to  a 
point  directly  under  the  centre  of  gravity  of  the  load,  and  such 
a  line  should  always  pass  above  the  axle  of  the  fore  wheels. 

Broad  JVJieels. — Much  controversy  has  existed  in  regard  to 
the  comparative  utility  of  wheels  having  a  broad,  or  a  narrow 
circumference.  The  disadvantages  of  broad  wheels  are,  that 
they  are  heavier  than  narrow  ones,  that  they  are  more  expensive, 
and  that  they  include  in  their  path  a  greater  number  of  stones  or 
projecting  obstacles.  Their  advantages  are,  that  they  pass  more 
easily  over  ruts  and  holes,  and  that  in  soft  and  sandy  roads  they 
sink  to  a  smaller  depth,  f    But  the  great  benefit  which  results 

*  Treatise  on  Mechanics,  vol.  ii.  p.  18. 

t  The  latter  advantage,  however,  is  of  a  more  equivocal  kind  than  appears 
at  first  view  ;  for  although  they  sink  less  deeply,  they  displace  more  earth  in 
sinking  to  the  same  depth.  Still,  however,  the  advantage,  upon  calculation, 
remains  on  the  side  of  the  hroad  wheel 


AIITS  OF  t.OCOMOTlON. 


199 


from  broad  wheels  is  of  an  indirect  kind,  and  arises  from  the 
improvement  of  tlie  roads  which  takes  place  under  their  use. 
They  tend  to  prevent  deep  and  narrow  ruts,  and  act  as  rollers 
in  levelling  the  surface. 

Form  of  Wheels. — If  roads  were  in  all  cases  level  and 
smooth,  wheels  should  be  made  exactly  cylindrical,  or  with  all 
their  spokes  parallel  to  the  same  plane.  But  since  the  unequal 
surface  of  most  roads  exposes  carriages  to  frequent  and  sudden 
changes  of  position,  it  is  found  advantageous  to  make  the  wheels 
a  little  conical,  or  as  it  is  commonly  termed,  dishing^  so  that  the 
spokes  may  all  diverge  with  their  extremities  from  the  carriage. 
In  this  case,  whenever  the  carriage  is  thrown  into  an  inclined 
position,  and  the  centre  of  gravity  shifted  towards  one  wheel, 
the  spokes  on  the  under  side  of  that  wheel  become  more  near- 
ly vertical,  and  are  in  a  more  advantageous  position  to  sustain 
the  pressure.  This  will  be  seen  in  Fig.  1,  at  the  bottom 
of  the  page.  In  muddy  roads  there  is  a  convenience  attend- 
ing the  dished  wheel,  in  having  its  circumference  further  from 
the  body  of  the  carriage,  than  that  of  a  straight  wheel  upon  the 
same  hubb  ^  would  be.  Some  disadvantages  at  the  same  time 
attend  upon  this  form  of  the  wheel,  the  principal  of  which  is, 
the  increase  of  friction  which  it  occasions.  A  conical  wheel,  if 
left  to  itself,  tends  to  travel  in  a  circle  round  a  point  where  the 
apex  of  the  cone  would  be  situated. .  If  it  is  obliged  to  advance 
in  a  straight  line,  it  has  a  degree  of  lateral  motion  and  friction, 
which  increases  in  proportion  as  it  deviates  from  the  cylindrical 
form.  In  common  cases,  a  slight  degree  of  the  dishing  form  is 
best,  but  it  should  never  be  carried  to  such  an  extent  as  to 
create  much  friction,  or  endanger  the  bending  of  the  spokes. 

Fio-.  1. 
A       °  B 

In  the  opposite  figure  A  represents  the  // 1  7/  il 
cylindrical,  and  B  the  dished  form  of  the  ir^^^jSl 

*  This  word,  instead  of  nave,  is  so  generally  used  in  this  country,  that  it 
would  be  a  useless  refinement  to  avoid  it.  The  same  is  true  of  the  woid  fac- 
tory for  manufactory,  and  also  of  many  mechanical  terms. 


200 


ARTS  OF  LOCOMOTION. 


Axletrces. — When  wheels  are  perfectly  upright,  the  ends  of 
the  axles  should  be  cylindrical,  but  in  dished  wheels  they  are 
made  conical  and  inclined  downward  so  as  to  make  their  under 
surface  horizontal.  In  lliis  case  the  wheels  spread  most  at  top, 
and  the  lower  spokes  are  most  nearly  vertical.  The  ends  of 
tlie  axletree  are  often  inclined  a  litde  forward,  which  arrange- 
ment causes  the  wheels  to  run  inward,  and  prevents  them  from 
pressing  on  the  linch  pin.  The  friction,  however,  is  increased. 
In  some  locomotive  carriages,  the  axle  is  fixed  to  both  wheels, 
and  turns  with  them.  This  mode  of  connexion  causes  great 
strain  and  friction,  whenever  the  path  is  in  any  other  than  a 
straight  line,  from  the ,  necessity,  which  is  produced,  that  the 
wheels  should  keep  pace  with  each  other  in  their  revolutions. 

Springs. — The  effect  of  suspending  a  carriage  on  springs,  is 
to  equalize  the  motion,  by  causing  every  change  to  be  more 
gradually  communicated  to  it,  and  to  obviate  shocks  by  con- 
verting percussion  into  pressure.  Springs  are  not  only  useful 
for  the  convenience  of  passengers,  but  they  also  diminish  the 
labor  of  draught ;  for  whenever  a  wheel  strikes  a  stone,  it  rises 
against  the  pressure  of  the  spring,  in  many  cases  without  mate- 
rially disturbing  the  load,  whereas,  without  the  spring,  the  load, 
or  a  part  of  it,  must  rise  with  every  jolt  of  the  wheel,  and  will 
resist  this  change  of  place  with  a  degree  of  inertia  proportion- 
ate to  the  weight  and  the  suddenness  of  the  percussion.  Hence 
springs  are  highly  useful  in  baggage  waggons  and  other  vehicles 
used  for  heavy  transportation.  ^ 

Attaching  of  Horses. — Horses  draw  most  advantageously 
when  they  are  either  single,  or  harnessed  abreast  of  each  other. 
When  two  horses  draw  side  by  side,  they  are  equally  near  to 
the  load,  and  have  the  same  line  of  traction.  If  their  traces 
are  attached,  as  is  frequently  done,  to  hooks  on  the  ends  of  a 
crossbar,  which  in  its  turn  is  connected  to  the  carriage  by  a 
staple  projecting  behind,  a  compensation  will  be  thus  made 
for  any  difference  in  the  strength  or  activity  of  the  animals. 

*  See  a  paper  by  Mr  Gilbert,  in  Brande's  Journal,  vol.  19. 


ARTS  OF  LOCOMOTION. 


201 


In  Fig.  2,  the  centre  E  upon  which  the  bar  moves  is  consider- 
ably behind  the  points  of  attachment,  A  and  B.  Hence  when 
one  end  falls  back,  so  that  the  arm  A  B  assumes  the  position 
C  D,  die  foremost  horse  will  have  Fig.  2. 

the  disadvantage  of  acting  by  a  j 
lever  equal  only  to  E  F,  while  the  j 

other  horse  acts  by  a  lever  equal  jiik  jr-M^-»^j^ 
to  EC.  In  the  narrow  streets  of  ^'  je P 
cities  a  custom  has  arisen  of  harnessing  draught  horses  before 
each  other  in  a  single  line,  probably  for  the  sake  of  room  and 
the  convenience  of  the  driver.  But  in  this  situation  only  the 
shaft  horse  has  an  advantageous  line  of  draught.  The  remain- 
ing horses  draw  nearly  in  a  horizontal  line,  and  of  course  at  a 
disadvantage.  Besides  this,  the  foremost  horses  being  attached 
to  the  ends  of  the  shafts,  do  not  act  directly  upon  the  load,  but 
expend  a  part  of  their  force  in  vertical  pressure  upon  the  back 
of  the  shaft  horse,  which  is  increased  in  drays,  sleds,  and  all 
low  carriages.    This  will  be  seen  by  inspecting  Fig.  3,  where 

Fig.  3. 


it  is  obvious  that  the  line  of  draught  of  the  first  horse  cannot 
become  direct,  without  crippling  down  the  shaft  horse.  The 
best  mode  of  remedying  this  difficulty,  would  apparently  be,  to 
attach  the  traces  of  the  forward  horse  to  a  strong  hook  project- 
ing downward  from  the  end  of  each  shaft,  so  as  to  bring  the 
traces  into  the  proper  line  of  traction,  by  directing  them  more 
nearly  towards  the  centre  of  the  wheels.  It  is  true  that  the 
shaft  horse  derives  a  certain  degree  of  mechanical  advantage 
from  vertical  pressure,  like  that  which  would  result  from  an 
increase  of  his  weight.  Yet  this,  although  useful  in  short  ex- 
ertions, is  not  so  when  continued  through  a  day's  fatigue. 


26 


202 


ARTS  OF  LOCOMOTION. 


HIGHWAYS. 

Roads. — Roads  intended  for  the  passage  of  wheel  carriages 
are  made  more  level  and  of  harder  materials,  than  the  rest  of 
the  ground.  In  roads,  the  travel  on  which  does  not  authorize 
great  expense,  natural  materials  alone  are  employed,  of  which 
the  best  are  hard  gravel,  and  very  small  stones.  The  surface 
of  roads  should  be  nearly  flat,  with  gutters  at  the  sides  to  facil- 
itate the  rxinning  off  of  water.  If  the  surface  is  made  too  con- 
vex, it  throv/s  the  weight  of  the  load  unequally  upon  one  wheel, 
and  also  that  of  the  horses  on  one  side,  whenever  the  carriage 
takes  the  side  of  the  road.  Hence  drivers  prefer  to  take  the 
middle  or  top  of  the  road,  and  by  pursuing  the  same  track  oc- 
casion deep  ruts.  The  prevention  of  ruts  is  best  effected  by 
flat  and  sohd  roads,  and  by  the  use  of  broad  wheels.  It  would 
also  be  further  effected  if  a  greater  variety  could  be  introduced 
in  the  width  of  carriages.  Embankments  at  the  sides  to  keep 
the  earth  from  sliding  down,  are  best  made  by  piling  sods  upon 
each  other,  like  bricks,  with  the  grassy  surface  at  right  angles 
with  the  surface  of  the  bank.  But  stone  walls  are  preferable 
for  this  purpose,  when  the  material  can  be  readily  obtained. 

Pavements. — Pavements  are  stone  coverings  of  the  ground, 
chiefly  employed  in  populous  cities  and  the  most  frequented 
roads.  Among  us  they  are  made  of  pebbles  of  a  roundish  form 
gathered  from  the  sea  beach.  They  should  consist  of  the 
hardest  kinds  of  stone,  such  as  granite,  sienite,  &£c.  If  flat 
stones  are  used,  they  require  to  be  artificially  roughened,  to 
give  secure  foothold  to  horses.  In  Milan,  and  some  other  pla- 
ces, tracks  for  wheels  are  made  of  smooth  stones,  while  the 
rest  of  the  way  is  paved  with  small  or  rough  stones.  ^ 

The  advantage  of  a  good  pavement  consists  not  only  in  its 
durability,  but  in  the  facility  with  which  transportation  on  it  is 

*  The  streets  of  many  of  the  ancient  cities  were  paved,  as  those  of  Rome, 
Pompeii,  &c.  But  the  streets  of  London  were  not  paved  in  the  eleventh  cen- 
tury, nor  those  of  Paris  in  the  twelfth. 


ARTS  OF  LOCOMOTION. 


203 


effected.  Horses  draw  more  easily  on  a  pavement,  than  on  a 
common  road,  because  no  part  of  their  power  is  lost  in  chang- 
ing the  form  of  the  surface.  The  disadvantages  of  pavements 
consist  in  their  noise,  and  in  the  wear  which  they  occasion  of 
the  shoes  of  horses,  and  tires  of  wheels.  They  should  never 
be  made  of  pebbles  so  large  as  to  produce  much  jolting  by  the 
breadth  of  the  interstices.  * 

McAdam  Roads. — The  system  of  road-making  which  takes 
its  name  from  Mr  McAdam,  combines  the  advantages  of  the 
pavement  and  gravel  road.  The  McAdam  roads  are  made  en- 
tirely of  hard  stones,  such  as  granite,  flint,  &ic.,  broken  up  with 
hammers  into  small  pieces  not  exceeding  an  inch  in  diameter. 
These  fragments  are  spread  upon  the  ground  to  the  depth  of 
from  six  to  ten  inches.  At  first  the  roads  thus  made  are  heavy 
and  laborious  to  pass,  but  in  time  the  stones  become  consolidat- 
ed and  form  a  mass  of  great  hardness,  smoothness,  and  perma- 
nency. The  stones  become  partly  pulverized  by  the  action  of 
carriage  wheels,  and  partly  imbedded  in  the  earth  beneath  them. 
The  consohdation  seems  to  be  owing  to  the  angular  shape  of 
the  fragments,  which  prevents  them  from  rolling  in  their  beds, 
after  the  insterstices  between  them  are  filled.  Mr  McAdam 
advises  that  no  other  material  should  be  added  to  the  broken 
stones,  apparently  with  a  view  to  prevent  the  use  of  clay  and 
chalk  which  abound  in  England.  It  appears,  however,  that  a  little 
clean  gravel  spread  upon  the  stones,  causes  them  to  consolidate 
more  quickly,  and  has  the  good  effect  of  excluding  the  hght 
street  dirt,  which  otherwise  never  fails  to  become  incorporated 
in  large  quantities  among  the  stones. 

*  Mr  Telford  has  constructed  in  England,  a  kind  of  paved  road,  in  which 
the  foundation  consists  of  a  pavement  of  rough  stones  and  fragments,  having 
their  points  upward.  These  are  covered  with  very  small  stone  fragments  and 
gravel,  for  the  depth  of  four  inches,  the  whole  of  which,  when  rammed  down 
and  consolidated,  forms  a  hard,  smooth,  and  durahle  road. 


204 


ARTS  OF  LOCOMOTION. 


BRIDGES. 

The  construction  of  small  bridges  is  a  simple  process,  while 
that  of  large  ones,  is,  under  certain  circumstances,  extremely 
difficult,  owing  to  the  fact  that  the  strength  of  materials  does 
not  increase  in  proportion  to  their  weight,  and  that  there  are 
limits  beyond  which  no  structure  of  the  kind  could  be  carried, 
and  withstand  its  own  gravity.  Bridges  differ  in  their  construc- 
tion and  in  the  materials  of  which  they  are  composed.  The 
principal  varieties  are  the  following. 

1.  Wooden  Bridges. — These,  when  built  over  shallow  and 
sluggish  streams,  are  usually  supported  upon  piles  driven  into 
the  mud,  at  short  distances,  or  upon  frames  of  timber.  But  in 
deep  and  powerful  currents  it  is  necessary  to  support  them  on 
strong  stone  piers  and  abutments,  built  at  as  great  a  distance  as 
practicable  from  each  other.  The  bridge  between  these  piers 
consists  of  a  stiff  frame  of  carpentry,  so  constructed  with  refer- 
ence to  its  material,  that  it  may  act  as  one  piece,  and  may  not 
bend,  or  break,  with  its  own  weight  and  any  additional  load  to 
which  it  may  be  exposed.  When  this  frame  is  straight,  the 
upper  part  is  compressed  by  the  weight  of  the  whole,  while  the 
lower  part  is  extended  like  the  tie  beam  of  a  roof.  But  the 
strongest  wooden  bridges  are  made  with  curved  ribs,  which  rise 
above  the  abutments  in  the  manner  of  an  arch,  and  are  not  sub- 
jected to  a  longitudinal  strain  by  extension.  These  ribs  are 
commonly  connected  and  strengthened  with  diagonal  braces, 
keys,  bohs,  and  straps  of  iron.  The  flooring  of  the  bridge  may 
be  either  laid  above  them,  or  suspended  by  trussing  underneath 
them.  Wooden  bridges  are  common  in  this  country,  and  some 
of  them  are  of  large  size.  One  of  the  most  remarkable  is  the 
upper  Schuylkill  bridge  at  Philadelphia,  which  consists  of  a 
single  arch,  the  span  of  which  is  340  feet. 

2.  Stone  Bridges. — These,  for  the  most  part,  consist  of 
regular  arches  built  upon  stone  piers  constructed  in  the  water, 
or  upon  abutments  at  the  banks.    Above  the  arches  is  made  a 


ARTS  OF  LOCOMOTION. 


205 


level  or  sloping  road.  From  the  nature  of  the  material  these 
are  the  most  durable  kind  of  bridges,  and  many  are  now  stand- 
ing which  were  built  by  the  ancient  Romans.  Several  of  the 
stone  bridges  across  the  Thames,  at  London,  are  distinguished 
for  elegance  and  strength.  The  stone  piers  on  which  bridges 
are  supported,  require  to  be  of  great  solidity,  especially  when 
exposed  to  rapid  currents,  or  to  floating  ice.  Piers  are  usually 
built  with  their  greatest  length  in  the  direction  of  the  stream, 
and  with  their  extremities  pointed  or  curved,  so  as  to  divide 
the  water  and  allow  it  to  glide  easily  past  them.  In  building 
piers  it  is  often  necessary  to  exclude  the  water  by  means  of  a 
coffer  dam.  This  is  a  temporary  inclosure  formed  by  a  double 
wall  of  piles  and  planks  having  their  interval  filled  with  clay. 
The  interior  space  is  made  dry  by  pumping,  and  kept  so  till 
the  structure  is  finished. 

3.  Cast  Iron  Bridges. — These  have  been  constructed  in 
England  out  of  blocks  or  frames  of  cast  iron,  so  shaped  as  to  fit 
into  each  other,  and  collectively  to  form  ribs  and  arches. 
These  bridges  possess  great  strength,  but  are  liable  to  be  dis- 
turbed by  the  expansion  and  contraction  of  the  metal  with  heat 
and  cold. 

4.  Suspension  Bridges. — In  these  the  flooring,  or  main  body 
of  the  bridge,  is  supported  on  strong  iron  chains,  or  rods,  hang- 
ing in  the  form  of  an  inverted  arch  from  one  point  of  support 
to  another.  The  points  of  support  are  the  tops  of  strong  pillars, 
or  small  towers,  erected  for  the  purpose.  Over  these  pillars 
the  chain  passes,  and  is  attached  at  each  extremity  of  the 
bridge  to  rocks  or  massive  frames  of  iron  firmly  secured  under 
ground.  The  great  advantage  of  suspension  bridges  consists 
in  their  stability  gf  equilibrium,  in  consequence  of  which  a 
smaller  amount  of  materials  is  necessary  for  their  construction, 
than  for  that  of  any  other  bridge.  If  a  suspension  bridge  be 
shaken,  or  thrown  out  of  equilibrium,  it  returns  by  its  w^eight  to 
its  proper  place,  whereas  the  reverse  happens  in  bridges  which 
are  built  above  the  level  of  their  supporters.  One  of  the  most 
remarkable  suspension  bridges,  is  that  over  the  Menai  Strait  on 


206 


ARTS  OF  LOCOMOTION. 


the  coast  of  Wales,  the  span  of  which,  or  rather  the  water  way, 
is  500  feet,  and  the  distance  between  the  points  of  support,  or 
centre  of  the  pieces,  560  feet.  It  is  suspended  by  four  wrought 
iron  cables  which  pass  over  rollers  on  the  tops  of  the  pillars,  and 
are  fixed  to  iron  frames  under  ground  which  are  kept  down  by 
masonry. 

5.  Floating  Bridges. — Upon  deep  and  sluggish  w^ater,  sta- 
tionary rafts  of  timber  are  sometimes  employed,  extending 
from  one  shore  to  another,  and  covered  with  planks,  so  as  to 
form  a  passable  bridge.  In  military  operations,  temporary 
bridges  are  often  formed  by  planks  laid  upon  boats,  pontoons, 
and  other  buoyant  supporters. 

RAIL  ROADS. 

In  the  best  constructed  public  roads,  a  great  amount  of  pow- 
er is  expended  in  overcoming  the  disadvantages  which  are  in- 
separable from  their  construction,  and  the  nature  of  their  mate- 
rials. The  chief  loss  of  power  depends  on  the  continual  change 
of  form  which  carriages  occasion  in  roads,  by  the  crushing  of 
stones,  cutting  of  ruts,  and  other  displacements  of  the  material 
of  which  the  road  is  made  ;  which  processes  serve  to  consume 
power,  without  forwarding  the  progress  of  the  carriage. 

The  object  of  a  rail  road  is  to  furnish  a  hard,  smooth,  and 
unchanging  surface  for  wheels  to  run  upon.  These  surfaces, 
in  most  cases,  consist  of  parallel  rails  of  iron,  raised  a  little 
above  the  general  level  of  the  ground,  and  having  a  gravelled 
road  between  the  rails,  so  that  the  rail  road  combines  the  ad- 
vantages of  good  foothold  for  horses,  and  of  smooth,  hard  sur- 
faces for  the  wheels  to  roll  upon.  The  wheels  are  made 
smooth  and  true,  and  guides,  to  prevent  them  from  slipping  off, 
are  affixed  either  to  the  wheels,  or  to  the  rails. 

Rail  roads  are  a  modern  invention,  and  their  greatest  im- 
provements have  been  made  within  the  present  century.  In 
comparing  the  efiect  of  a  rail  road  with  that  of  a  common  turn- 
pike road,  a  saving  is  made,  according  to  Mr  Tredgold,  *  of 

*  Treatise  on  Rail  Roads  and  Carriages,  p.  3. 


ARTS  OF  LOCOMOTION. 


207 


seven  eighths  of  the  power,  one  horse  on  a  rail  road  producing 
as  much  effect  as  eight  horses  on  a  turnpike  road.  In  the  ef- 
fect produced  by  a  given  power,  the  rail  road  is  about  a  mean 
between  the  turnpike  road  and  a  canal,  when  the  rate  is  about 
three  miles  per  hour ;  but  when  greater  speed  is  desirable,  the 
rail  road  may  equal  the  canal  in  effect,  and  even  surpass  it. 

The  earliest  rail  roads  appear  to  have  been  constructed  of 
wood  only.  But  at  the  present  day  iron  is  employed  in  all 
rails  from  which  durability  is  expected.  In  some  chies  tracks 
of  hewn  stone  are  laid  for  wheels  in  the  streets,  but  these  are 
seldom  executed  with  sufficient  accuracy  to  deserve  the  name 
of  railways.  Of  the  iron  rail  road,  there  are  three  principal 
varieties.  1.  The  Edge  rail.  2.  The  Tram  road.  3.  The 
Single  rail. 

Edge  Railway. — In  this  species  the  rails  are  laid  with  the 
edge  upward,  and  the  carriage  is  retained  upon  them  by  a 
flange,  or  projecting  edge,  attached  to  the  wheels,  instead  of  the 
rail.  These  rails,  when  made  of  cast  iron,  are  commonly  about 
three  feet  long,  and  four  or  five  inches  deep  in  the  middle,  the 
outline  being  curved  on  the  under  side,  to  produce  equality  of 
strength.  Fig.  4  represents  a  side  view  of  a  common  cast  iron 
railway.    The  ends  of  the  rails  are  received  in  a  piece  of  cast 

Fig.  4. 


iron,  called  a  chair,  and  these  chairs  are  affixed  to  large  blocks 


of  stone  with  a  broad  base, 
called  sleepers,  which  are 
previously  placed  in  the 
ground  upon  a  proper  level. 
Fig.  5  is  a  section,  or  end 
view  of  the  rail  road,  togeth- 
er with  the  wheels  of  a  car- 
riage, and  the  flange  which  ^^P^ 
serves  to  guide  them. 


Fig.  5. 


208 


ARTS  OF  LOCOMOTION. 


Rails  are  now  frequently  made  of  wrought  iron  with  a  form 
nearly  similar  to  that  which  has  been  represented.  As 
this  material  is  costly  when  employed  alone,  it  is  sometimes 
used  in  thin  bars  as  a  covering  to  wooden  rails,  particularly  in 
this  country  where  timber  is  plenty,  and  iron  expensive.  *  An- 
other and  a  better  method  has  been  adopted  of  laying  straight 
bars  of  wrought  iron  upon  tracks  of  hammered  granite. 
Wrought  iron  rails  have  the  advantage  of  reducing  the  number 
of  joints,  a  circumstance  which  greatly  increases  the  strength, 
as  well  as  smoothness  of  the  road.  The  comparative  durability 
of  wrought,  and  of  cast  iron  rails,  is  as  yet  not  fully  settled. 

Tram  Road. — Tram  roads  are  flat  rails,  made  usually  of 
cast  iron,  with  an  elevated  edge  or  flange,  on  one  side,  to  guide 
the  wheels  of  carriages  in  their  path.  Tram  rails  are  weaker 
than  edge  rails,  when  made  of  the  same  amount  of  material, 
and  it  is  sometimes  necessary  to  strengthen  them  with  ribs  un- 
derneath. They  are  capable  of  being  used  for  ordinary  wheel 
carriages,  but  the  introduction  of  wheels  which  are  not  perfect- 
ly smooth,  is  always  injurious  to  the  road.  Tram  roads  are 
more  liable  to  be  covered  with  dirt  than  rails  of  other  kinds. 

Single  Rail. — Carriages  may  be  made  to  run  upon  a  single 
rail,  by  elevating  the  rail  from  the  ground,  and  suspending  the 
load  beneath  it.  In  Mr  Palmer's  railway,  the  rail  is  about 
three  feet  above  the  surface  of  the  ground,  and  is  supported  by 
pillars  placed  at  distances  of  about  nine  feet  from  each  other. 
The  carriage  consists  of  two  receptacles,  or  boxes,  suspended 
one  on  each  side  of  the  rail  by  an  iron  frame,  and  having  two 
wheels  placed  one  before  the  other.  The  rims  of  the  wheels 
are  concave,  and  fit  the  convex  surface  of  the  rail,  and  the  cen- 
tre of  gravity  of  the  carriage,  whether  loaded  or  empty,  is  so 
far  below  the  upper  edge  of  the  rail,  that  the  receptacles  hang 
in  equilibrium,  and  will  bear  a  considerable  inequality  of  load 
without  inconvenience,  owing  to  the  change  of  fulcrum  allowed 
by  the  breadth  of  the  rail,  which  is  about  four  inches.  The 

*  The  durability  of  this  combination  of  wood  and  iron,  remains  to  be  settled 
by  longer  experience. 


ARTS  OF  LOCOMOTION. 


209 


alleged  advantages  of  the  single  rail  are,  that  it  is  more  free 
from  lateral  friction  than  the  other  kinds  of  railway,  and  that 
being  higher  from  the  ground,  it  is  less  hable  to  be  covered 
with  dust  and  gravel,  and  lastly  that  it  is  more  economical,  the 
construction  of  one  rail  being  less  expensive  than  of  two.  * 

Passings. — When  the  amount  of  travel  on  a  rail  road  is  very 
great,  it  becomes  necessary  that  the  road  should  be  double, 
one  set  of  tracks  being  provided  for  carriages  moving  in  each 
direction.  Where  there  is  less  travel,  a  single  road  is  sufficient, 
if  it  be  provided  with  double  places,  called  sidelings,  for  carria- 
ges to  pass  each  other  at  convenient  distances.  But  in  both 
cases  the  travelling  is  liable  to  be  retarded  by  the  difficulty 
which  exists,  during  a  great  part  of  the  way,  for  carriages  to 
pass  each  other  when  moving  in  the  same  direction,  those  of 
slow  motion  obstructing  the  progress  of  those  which  are  intend- 
ed for  greater  speed.  In  order  to  obviate  this  difficulty,  and 
also  to  diminish  the  number  of  passing  places,  Mr  Treadwell 
proposes  f  to  regulate  the  times  of  starting  in  both  directions, 
and  also  the  velocity  of  the  faster  and  the  slower  carriages,  by 
a  uniform  arrangement,  so  that  they  shall  always  move  in  con- 
cert and  meet  at  the  passing  places  at  stated  times,  and  at  no 
other  times  or  places.  By  an  easy  calculation  the  more  rapid 
vehicles  may  be  so  regulated  as  to  overtake  the  slower  ones 
exactly  at  the  passing  places,  and  a  coach  moving  at  the  rate 
of  nine  miles  an  hour,  may  experience  no  hindrance  from  a 
multitude  of  waggons  moving  with  a  third  part  of  the  velocity. 

When  forks  in  a  rail  road  occur,  at  the  passing  places,  or 
elsewhere,  a  part  of  the  rails  is  rendered  moveable,  so  as  to  di- 
rect the  wheels  upon  either  track.  When  the  railway  crosses 
a  public  road,  it  is  made  to  pass  at  a  lower  level  than  the  com- 
mon surface,  and  is  protected  from  carriage  wheels  by  an  elevat- 
ed edging  of  wood  or  stone ;  but  when  the  single  rail  crosses  a 

*A  railway  of  this  kind  v»-as  invented  more  than  twent)''  5^earp  a^o,  by 
Henry  Sargent,  Esq.  of  Boston, 
t  Franklin  Journal,  vol.  iv.  p.  278. 

27 


210 


ARTS  OF  LOCOMOTION. 


road,  a  part  of  it  must  be  made  to  swing  open  like  a  turnpike 
gate.  Railways  require  to  be  kept  as  free  as  possible  from  dirt, 
which  greatly  increases  the  resistance.  Mr  Palmer  found  upon 
a  tram  road,  that  it  required  19  per  cent,  more  power  to  draw 
the  same  carriages  when  the  rails  were  slightly  covered  with 
dust,  than  when  they  were  swept  clean. 

Propelling  Power, — Horses  are  commonly  employed  for 
drawing  loads  upon  railways,  a  horse  being  supposed  capable 
of  drawing  eight  times  as  much,  as  upon  a  common  road. 
Locomotive  steam  -engines  are  much  employed  upon  railways, 
in  England.  They  were  at  first  made  to  propel  carriages  by 
means  of  a  toothed  wheel,  which  acted  upon  a  rack  attached 
to  one  of  the  rails ;  but  at  the  present  day,  they  are  made  to 
act  by  the  friction  only  of  the  carriage  wheels  upon  the  plain 
rail.  These  engines  are  always  made  of  high  pressure, 
since  those  of  low  pressure  are  rendered  too  heavy  by  the 
weight  of  the  water  necessary  for  condensation.  It  has 
been  proposed  to  place  stationary  engines  at  short  distances, 
which  should  draw  carriages  forward  from  one  to  the  other  by 
endless  chains,  thus  saving  the  transportation  of  the  engines. 
Where  the  declivity  of  the  road  is  great,  loaded  carriages  some- 
times descend  by  their  own  gravity,  and  at  the  same  time  draw 
up  the  empty  ones  by  means  of  puUies.  To  prevent  carriages 
from  acquiring  too  great  a  velocity  in  descending,  a  crooked 
lever,  called  a  brake  or  convoy^  is  applied  to  the  surface  of  the 
wheels,  so  as  to  retard  them  by  its  friction.  *  When  loaded 
carriages  are  transferred  from  one  part  of  the  road,  to  another 
of  greater  elevation,  they  are  either  drawn  up  an  inclined  plane 
with  ropes,  by  horses,  or  stationary  engines ;  or  they  may  be 
lifted  perpendicularly,  by  pullies. 

*  A  retarding  friction  is  produced,  when  necessary,  in  mountainous  countries, 
upon  common  roads,  by  chaining  one  of  the  wheels,  when  the  carriage  goes 
down  hill,  so  as  to  prevent  its  turning.  The  same  effect  is  produced  in  a  safer 
manner,  by  placing  a  wooden  shoe  like  a  runner,  under  one  of  the  wheels. 


AKTS  OF  LOCOMOTION. 


211 


CANALS. 

Canals  are  artificial  channels  for  water,  cut  for  the  purpose 
of  admitting  inland  navigation.  The  great  utility  of  canals  in 
facilitating  transportation,  has  caused  them  to  be  constructed  in 
all  ages.  The  canals  of  the  ancients  were  chiefly  made  on  one 
level,  so  as  to  form  merely  artificial  rivers,  or  creeks.  Those 
of  the  moderns,  by  means  of  locks,  are  carried  indiscriminately 
over  ground  which  is  depressed  or  elevated.  In  level  tracts  of 
country,  if  the  earth  is  of  suitable  character,  canals  are  easily 
made.  But  in  loose  and  crumbling  soils,  in  undulating,  rocky, 
and  mountainous  tracts,  and  in  those  which  are  intersected  by 
large  streams ;  their  construction  becomes  expensive  and  diffi- 
cult. To  surmount  these  difficulties,  loose  soils  are  defended 
with  firmer  materials,  vallies  are  passed  by  enbankments,  hills 
are  penetrated  by  deep  cuttings  or  tunnels,  rivers  are  crossed 
with  aqueducts,  and  declivities  are  ascended  and  descended  by 
locks.  In  order  that  water  may  not  be  wanting  in  any  part  of 
the  canal,  a  supply  is  insured  at  the  highest  level,  and  this  grad- 
ually passes  off  through  the  locks,  to  the  lowest.  The  streams 
which  furnish  the  water  at  this,  and  other  points,  are  called 
feeders. 

Embankments. — Canals  are  dug  with  sloping  sides,  to  pre- 
vent the  banks  from  caving  in.  The  boats  being  in  almost  all 
cases  drawn  by  horses,  a  firm,  uninterupted  towing  path  is  form- 
ed on  one  of  the  banks.  The  banks  are  hable  in  time,  to  be- 
come indented  and  washed  away,  by  the  constant  agitation  of 
the  water,  occasioned  by  the  passage  of  boats.  To  prevent 
this,  they  are  sometimes  secured  by  driving  close  rows  of  stakes 
against  the  banks ;  but  the  only  effectual  protection  is  found  in 
walling  the  banks  with  stone.  When  the  canal  crosses  a  sec- 
tion of  country,  the  surface  of  which  is  lower  than  the  intended 
surface  of  the  water,  the  canal  is  raised  to  the  proper  level  by 
means  of  embankments.  These  are  artificial  banks,  or  dykes, 
made  of  such  materials  as  will  not  be  liable  to  leak,  and  of  such 


212 


ARTS  OF  LOCOMOTION. 


form  and  strength  that  they  will  not  be  broken  by  the  pressure 
of  the  water.  The  surface  of  these  banks  is  of  a  sloping  form, 
and  is  secured  by  sodding,  and  in  some  instances,  by  piles,  or 
stone  walls.  Where  the  nature  of  the  earth  renders  leakage 
probable,  it  is  common  to  cover  the  bottom  and  sides  of  the 
canal  with  a  lining  of  puddle,  which  is  formed  from  loam,  or 
clay  and  gravel,  worked  up  with  water.  For  additional  securi- 
ty a  trench  is  dug  in  each  bank  to  a  greater  depth  than  the 
bottom  of  the  canal,  and  filled  with  puddle. 

It  sometimes  happens  that  the  embankments  act  as  a  dam  to 
prevent  the  land  on  one  side  of  the  canal,  from  being  properly 
drained.  In  this  case,  culverts,  or  subterranean  passages  are 
constructed  underneath  the  canal,  but  not  communicating  with 
it;  to  effect  the  necessary  draining.  Culverts  are  made  of 
brick  or  stone,  and  require  to  be  strong  and  tight. 

Aqueducts, — When  a  canal  crosses  a  river,  or  a  deep  ravine, 
it  is  supported  at  the  proper  level  by  an  aqueduct.  This  struc- 
ture resembles  a  stone  bridge,  formed  of  strong  piers  and  arch- 
es, of  regular  masonry,  rendered  as  tight  as  possible  with  hy- 
draulic cement.  Upon  the  top,  a  level  channel  for  the  water 
is  formed.  This  is  secured  with  strong  and  tight  walls  on 
the  sides,  and  lined  within  by  a  coating  of  clay.  Room  for 
the  towing  path  must  be  preserved,  on  one  of  the  sides.  In 
England,  aqueducts  have  sometimes  been  made  of  cast  iron. 

Tunnels. — Tunnels  are  subterranean  passages,  most  fre- 
quently cut  through  the  base  of  hills,  to  afford  a  level  water 
course  for  canals.  Tunnels  are  also  made  for  the  passage  of 
railways,  and,  in  some  cases,  of  highway  roads.  When  they 
are  obliged  to  be  cut  through  solid  rock,  which  is  done  chiefly 
by  blasting,  their  formation  is  difficult,  but  they  require  no  ar- 
tificial security  for  their  subsequent  protection.  But  tunnels 
which  are  made  in  soft  earth,  require  to  be  arched  over  for 
their  whole  length  with  stone  or  brick ;  and  in  loose,  springy 
ground,  the  bottom  likewise  must  be  defended  with  an  inverted 
arch.  That  tunnels  may  be  properly  ventilated,  especially 
while  digging,  shafts  or  vertical  passages  are  sunk  at  proper  dis- 


ARTS  OF  LOCOMOTION. 


213 


tances,  in  which  fires  are  kept  burning  to  create  a  current  for 
discharging  the  foul  air.  One  of  the  most  remarkable  tunnels 
is  that  at  Worsley,  on  the  Duke  of  Bridgewater's  canal,  which 
with  all  its  branches  is  estimated  at  eighteen  miles  in  length. 

Gates  and  Weirs, — As  all  canals  are  liable  to  have  their 
banks  broken  through  during  violent  rains  and  freshets,  it  is  im- 
portant to  lessen  the  injury  which  results  from  such  accidents, 
by  retaining  as  much  of  the  water  in  the  canal  as  possible.  To 
effect  this  object,  safety  gates  and  stop  gates,  are  placed  at 
suitable  distances  from  each  other,  on  the  canal,  so  that  by 
closing  them  at  any  time  in  case  of  accident,  the  escape  of  that 
part  of  the  water  which  is  beyond  them,  may  be  prevented. 
These  gates  are  sometimes  attached  to  the  sides,  and  some- 
times lie  upon  the  bottom. 

Certain  parts  of  the  banks  called  weirs,  are  made  lower  than 
the  rest,  to  discharge  the  superfluous  water,  and  keep  the  sur- 
face at  a  proper  level.  To  prevent  them  from  being  gullied  or 
worn  away  by  the  attrition  of  the  water,  they  are  commonly 
made  of  stone,  or  sometimes  of  wood. 

Locks. — When  a  canal  changes  from  one  level  to  another  of 
different  elevation,  the  place  where  the  change  of  level  takes  place, 
is  commanded  by  a  lock.  Locks  are  tight  oblong  inclosures 
in  the  bed  of  the  canal,  furnished  with  gates  at  each  end,  which 
separate  the  higher  from  the  lower  parts  of  the  canal.  When 
a  boat  passes  up  the  canal,  the  lower  gates  are  opened,  and 
the  boat  glides  into  the  lock,  after  which  the  lower  gates  are 
shut.  A  sluice  communicating  with  the  upper  part  of  the  ca- 
nal is  then  opened,  and  the  lock  rapidly  fills  with  water,  elevat- 
ing the  boat  on  its  surface.  When  the  lock  is  filled  to  the 
highest  water  level,  the  upper  gates  are  opened,  and  the  boat, 
being  now  on  the  level  of  the  upper  part  of  the  canal,  passes 
on  its  way.  The  reverse  of  this  process  is  performed,  when 
the  boat  is  descending  the  canal. 

Locks  are  made  of  stone  or  brick,  sometimes  of  wood. 
The  walls  are  sometimes  erected  upon  an  inverted  arch,  and 
also  upon  piles,  if  the  soil  is  alluvial,  or  loose.    They  are  laid 


214 


ARTS  OF  LOCOMOTION. 


with  hydraulic  cement,  and  rendered  impervious  to  water. 
The  gates  are  commonly  double,  resembling  folding  doors, 
turning  upon  coin  posts  which  are  next  the  walls.  They  meet 
each  other  in  most  instances,  at  an  obtuse  angle,  and  the  pres- 
sure of  the  water  serves  to  keep  their  contact  more  firm.  The 
hydrostatic  pressure  in  these  cases,  being  in  full  force  in  a  di- 
rection perpendicular  to  the  surface  of  the  gates,  has  a  different 
action  from  that  of  the  pressure  of  gravity  applied  to  a  roof,  or 
similar  structure ;  and  gives  to  long  gates  a  greater  comparative 
disadvantage,  than  to  short  ones.  Cast  iron  gates  are  some- 
times used  in  England,  curved  in  the  form  of  a  horizontal  arch, 
with  their  convex  side  opposed  to  the  water.  Valves  are  small 
shding  shutters  which  admit  a  stream  of  water  for  the  purpose 
of  gradually  filling  or  emptying  the  lock,  to  prevent  the  shock 
of  suddenly  opening  the  gates. 

In  situations  where  there  is  a  scarcity  of  water,  the  waste 
occasioned  by  frequently  opening  the  gates  for  the  passage  of 
hoats,  is  too  great  for  the  amount  supplied  to  the  canal.  In 
these  cases,  to  economize  the  water,  reservoirs  are  provided  at 
different  heights  on  each  side  of  the  lock.  The  water  in  the 
upper  parts  of  the  lock,  is  discharged  into  these  reservoirs,  and 
only  that  in  the  lower  parts  is  suffered  to  escape  into  the  lower 
canal.  Afterwards,  the  water  in  these  reservoirs  is  used  to  fill 
tigain  the  lower  parts  of  the  lock,  and  thus  the  same  water  is 
made  use  of  a  second  time. 

In  China,  where  inland  navigation  is  much  practised,  it  is 
said  there  are  no  locks,  but  boats  are  transferred  from  one  lev- 
el to  another,  by  means  of  inclined  planes.  This  method  is 
sometimes  practised  in  Europe,  and  it  had  a  zealous  advocate 
in  the  late  Mr  Fulton.  To  effect  this  transfer  most  advanta- 
geously, two  boats  passing  in  opposite  directions,  are  connected 
together  by  a  chain  passing  over  a  pully.  One  boat  in  de- 
scending the  plane  assists  by  its  weight  to  draw  the  other  up- 
ward. Sometimes,  instead  of  inclined  planes,  perpendicular 
hfts  have  been  proposed,  by  which  the  boats  are  hoisted  direct- 
ly by  pullies  from  one  level  to  another,  or  lowered  in  the  op- 


ARTS  OF  LOCOMOTIQX. 


215 


posite  direction  by  the  same  means.  The  objection  to  all  these 
modes  exists  in  the  strain  to  which  the  boats  are  exposed,  un- 
supported by  the  pressure  of  the  water.  Various  expedients 
have  been  proposed  for  altering  the  level  of  the  water,  and 
transferring  boats,  by  means  of  large  plungers,  diving  chests, 
&;c.,  but  none  of  them,  as  yet,  appear  to  have  been  approved 
in  practice.  * 

Boats, — Canal  boats  are  made  narrow,  for  passing  each 
other,  and  draw  water  proportioned  to  the  depth  of  the  canaL 
Their  length  is  limited  only  by  that  of  the  locks.  They  are- 
drawn  by  horses  on  the  tow  path,  irig.  e. 
being  kept  by  the  rudder  from 
coming  in  contact  with  the  bank. 
No  species  of  oars,  poles,  or 
paddle  wheels  are  allowed,  on  account  of  the  injury  done  to  the 
bottoms  and  banks,  by  their  use.  It  is  said,  however,  that 
the  steam  engine  has  in  some  cases  been  used  without  injury 
to  the  canal,  by  causing  the  paddle  wheels  to  work  in  a  water 
pagsage,  or  casing,  which  passes  through  the  boat  above  its  bottom. 

Size  of  Canals. — Canals  differ  greatly  from  each  other,  not 
only  in  their  length,  but  their  size,  and  the  draught  of  water 
which  they  admit.  One  of  the  largest  canals,  as  far  as  the 
volume  of  water  is  concerned,  is  the  Great  Dutch  canal  which 
connects  the  city  of  Amsterdam  with  the  Helder,  on  the  north 
coast  of  Holland.  This  canal  is  50  miles  in  length,  124  feet 
in  width,  at  the  surface  of  the  water,  36  feet  wide  at  bottom^ 
and  about  21  feet  deep.  It  is  large  enough  to  permit  onefrig- 
ate  to  pass  another.  The  Caledonian  canal,  extends  from  the 
Murray  Frith,  on  the  eastern  coast  of  Scotland,  to  Loch 
Eil,  on  the  western,  and  admits  of  the  passage  of  large 
ships.  It  is  120  feet  wide  at  the  water  surface,  and  50  wide 
at  bottom.  The  depth  of  water  is  20  feet.  The  distance 
from  sea  to  sea,  is  about  59  miles,  of  which  37|  is  lake  naviga- 
tion, and  21^  is  cut.  f    The  Canal  of  Languedoc,  in  France, 

*  Repertory  of  Arts,  vol.  i,  ii,  and  xxiii. 

t  Supplement  to  the  Encyclopedia  Brittannica,  and  Edinburgh  Encyclopedia. 


216 


ARTS  OF  LOCOMOTION, 


is  64  leagues  in  length,  and  connects  the  Atlantic  ocean  with 
the  Mediterranean  sea.  It  is  64  feet  wide  at  the  surface  and 
navigable  for  vessels  of  100  tons.  The  great  New  York,  or  Erie 
Canal,  is  360  miles  long,  and  extends  from  the  Hudson  river,  at 
Albany,  to  Lake  Erie,  at  Buffalo.  It  is  40  feet  wide  at  the  sur- 
face, 28  feet  wide  at  bottom,  and  has  four  feet  depth  of  water. 


SAILING. 

Form  of  a  Ship. — The  movement  of  bodies  through  water, 
if  performed  within  certain  limits  of  velocity,  is  attended  with 
less  resistance  than  that  which  takes  place  in  most  other  modes 
of  transportation.  A  body,  however,  of  given  size  will  encoun- 
ter a  greater  or  less  resistance  from  the  water,  according  to  its 
proportions,  and  the  sort  of  surface  which  it  opposes  to  the 
fluid.  In  calculating  the  proper  form  for  a  ship,  it  is  necessary 
to  consider  the  kinds  of  pressure  to  which  bodies  moving  in 
fluids  are  subject.  If  we  suppose  an  oblong  square  box,  or 
parallelopiped,  as  A  B  C  D,  p^^,  ^ 

in  Fig  7,  to  move  through  ^4.  jg 

the  water  in  the  direction  of  ^   


its  length,  the  pressure  will  be 

increased  before,  and  diminish-  C  J} 

ed  behind  it,  the  surface  of  the  water  being  elevated  at  the  an- 
terior extremity,  and  depressed  at  the  posterior;  an  effect 
which  increases  in  a  high  ratio  as  the  velocity  becomes  greater. 
The  principal  part  of  the  water  which  is  before  the  moving 
body,  divides  and  passes  off  by  the  sides,  but  a  certain  quantity 
of  what  is  called  dead  water,  is  pushed  along  in  advance  of  the 
moving  body,  nearly  in  the  same  manner  as  if  it  were  a  part  of 
the  body  itself.  The  shape  of  this  dead  water  at  the  surface, 
is  found  to  be  that  of  an  irregular  triangle,  and  hence  it  becomes 
advantageous  to  add  to  the  moving  body  an  extremity,  or  how, 
having  nearly  the  same  shape  as  the  dead  water,  and  occupy- 
ing its  place,  as  in  the  dotted  line  BED.  On  the  other  hand, 
there  occurs  behind  the  moving  body  a  depression  of  surface, 


ARTS  OF  LOCOMOTION. 


217 


and  a  partially  empty  space,  which  is  also  of  a  triangular,  or 
wedge  form,  consisting  of  the  room  which  the  moving  hody  has 
just  left,  and  into  which  the  water  upon  each  side  has  not  yet 
flowed.  The  cavity  which  is  thus  formed,  resists  the  progres«r 
of  the  body  by  its  negative  pressure.  Its  effect  is  readily  un- 
derstood, when  we  consider  that  if  the  water  before  the  moving 
body  be  raised  one  foot,  while  the  water  behind  it  is  depressed 
one  foot,  the  difference  of  pressure  upon  the  two  extremities 
will  be  equal  to  that  resulting  from  two  feet.  On  this  account 
it  is  advantageous  to  add  to  the  moving  body  a  tapering,  or 
wedge-shaped  extremity  behind,  capable  of  occupying  this  cavi- 
ty and  nearly  answering  to  it  in  shape,  as  represented  by  the 
dotted  line  A  G  C.  The  consequence  will  be,  that  the  water, 
which  is  advancing  from  both  sides  to  fill  up  the  vacuity,  will 
meet  the  tapering  sides  of  the  vessel  soon  enough  to  ob- 
viate, or  greatly  diminish  the  negative  pressure.  The  form 
produced  by  this  general  outline,  varied  by  a  proper  curvature 
of  the  sides  and  bottom,  corresponds  nearly  to  that  which 
is  adopted  in  the  construction  of  ships,  and  also  to  that 
pursued  by  nature  in  the  structure  of  fishes.  If  a  vessel  be  in- 
tended for  a  fast  sailer,  its  proportionate  length  and  its  sharp- 
ness before  and  behind,  must  be  increased,  since  both  the  posi- 
tive and  negative  pressure,  and  the  extent  of  the  dead  water 
and  vacant  space,  will  increase  with  the  velocity. 

Keel  and  Rudder. — The  use  of  the  keel,  which  is  a  project- 
ing timber,  extending  the  whole  length  of  the  ship's  bottom,  is 
to  assist  in  confining  the  motion  of  the  ship  to  its  proper  direc- 
tion, and  by  its  lateral  resistance,  to  diminish  the  disposition  to 
roll  or  vibrate  from  side  to  side.  The  rudder,  which  is  a  per- 
pendicular part  attached  by  braces  resembhng  hinges,  to  the 
stern  post  of  the  vessel,  serves  to  govern  the  ship's  course,  by 
altering  the  relative  resistance  of  its  two  sides.  Thus,  while 
the  ship  is  under  way,  if  the  rudder  is  turned  to  one  side,  it  re- 
ceives an  impulse  from  the  water  on  that  side,  causing  the  stern 
to  turn  towards  the  opposite  side,  where  no  such  resistance  ex- 
28 


218 


ARTS  OF  LOCOMOTION. 


ists,  thus  altering  tlic  direction  of  the  keel,  and  the  general 
course  of  the  vessel. 

Effect  of  the  Wind. — When  a  ship  sails  in  the  same  direc- 
tion as  the  wind,  she  is  said  to  be  scudding^  or  sailing  before  the 
windy  and  if  she  had  but  one  sail,  it  would  act  with  the  greatest 
advantage,  when  perpendicular,  or  nearly  so,  to  the  wind. 

When  a  ship  advances  against  the  wind,  and  endeavours  to 
proceed  in  the  nearest  direction  possible  to  the  point  of  com- 
pass from  which  the  wind  blows,  she  is  said  to  be  close  hauled. 
A  large  ship  will  sail  against  the  wind  with  her  keel  at  an  an- 
gle of  six  points,  with  the  direction  of  the  wind,  and  sloops  and 
smaller  vessels  may  sail  much  nearer.  •  When  a  ship  is  neither 
sailing  before  the  wind,  nor  close  hauled,  she  is  said  to  be 
sailing  large.  In  this  case,  her  sails  are  set  in  an  oblique  posi- 
tion, between  the  direction  of  the  wind,  and  that  of  the  intend- 
ed course  ;  as  represented  in  the  various  plans  of  vessels  in 
Fig.  8,  where  the  direction  of  the  wind  is  represented  by  the 

Fig.  8. 


AUTS  OF  LOCOMOTION. 


01§ 


arrow,  and  the  position  of  the  yards  and  sails,  which  is  necessa- 
ry for  proceeding  on  the  various  points  of  compass,  is  shown  by 
the  transverse  lines  on  each  plan.  The  relation  of  the  wind  to 
the  course  of  the  vessel  is  determined  by  the  number  of  points 
of  the  compass  between  the  course  she  is  steering,  and  the 
course  which  she  would  be  steering,  if  close  hauled.    In  Fig. 

8,  the  ships  a  and  h  are  close  hauled,  and  the  ships  c  and  <Z, 
the  former  steering  east  by  north,  and  the  latter  west  by  north, 
have  the  wind  one  point  large.  The  ships  e  and/,  one  steer- 
ing east,  and  the  other  w^est,  have  the  wind  two  points  large. 
In  this  case,  the  wind  is  at  right  angles  with  the  keel,  and  is 
said  to  be  upon  the  beam.  The  ships  g  and  A,  steering  south 
east,  and  south  west,  have  the  wind  six  points  large,  or  as  it  is 
commonly  termed,  upon  the  quarter,  and  this  is  considered  as 
a  very  favorable  manner  of  sailing,  because  all  the  sails  coope- 
rate to  increase  the  ships  velocity,  whereas  when  the  wind  is 
directly  aft,  as  in  the  vessel  m,  it  is  partly  intercepted  by  the 
after  sails,  and  prevented  from  striking  with  its  full  force  on  those 
which  are  forward.  The  force  of  a  wind  which  strikes  obliquely 
upon  the  sails,  supposing  them  flat  surfaces,  is  resolvable  into 
two  forces,  one  of  which  tends  to  push  the  vessel  ahead,  and  the 
other  to  push  her  sideways.  If  the  form  of  the  vessel,  instead 
of  being  oblong,  were  circular,  like  a  tub,  she  would  move  in 
the  direction  of  the  diagonal  of  a  rectangle,  representing  these 
two  forces,  and  her  course  would  be  at  right  angles  with  the 
position  of  the  sail,  or  in  the  direction  of  the  line  A  B,  in  Fig. 

9.  But  owing  to  the  oblong  shape  of  the  vessel,  and  the  influ- 
ence of  her  keel,  it  requires  about  twelve  times  as  much  force 
to  push  her  sideways,  as  to  push  her  head  foremost.*  The 
oblique  impulse,  therefore,  will  carry  her  a  great  distance  for- 
ward, in  the  time  that  she  is  drifting  a  short  distance  to  the  lee- 
ward, and  it  is  this  relative  difference  of  progress  which  ena- 
bles a  vessel  to  advance  even  against  the  wind.  The  angular 
deviation  of  a  ship'sjreal  course  from  her  apparent  course 

*  Robison's  Mechanical  Philosophy,  vol.  iv.  p.  620. 


220 


ARTS  OF  LOCOMOTION. 


upon  which  her  head  is  directed,  is  called  the  leeway.  In  the 
vessel,  Fig  9,  with  the  wind  blowing  in  Fig.  9. 

the  direction  of  the  arrows,  and  the 
sails  set  as  represented,  if  the  vessel 
w^ere  moving  in  a  railway,  or  unchange- 
able channel,  her  course  would  be  B  D, 
but  in  the  water  she  drifts  so  much  to 
the  leeward,  that  her  real  course  is  B  C, 
and  the  angle  C  B  D,  represents  the  amount  of  leeway. 

Stability  of  a  Ship. — The  masts  of  a  ship,  when  acted  upon 
by  the  pressure  of  the  wind  against  the  sails,  are  so  many  lev- 
ers, the  tendency  of  which,  is,  to  overset  her.  To  counteract 
this  tendency,  a  sufficient  weight  of  ballast,  or  cargo,  is  stowed 
in  the  bottom  of  the  hold,  to  carry  the  centre  of  gravity  into  the 
lower  part  of  the  hull,  so  that  this  part  will  always  preponderate, 
while  the  relative  buoyancy  of  the  upper  part  causes  the  vessel 
to  right,  as  often  as  her  position  is  disturbed.  If  the  ballast  is 
too  light,  or  is  stowed  too  high  in  the  hold,  the  vessel  is  said  to 
be  too  crank,  and  rolls  more,  and  cannot  carry  so  much  sail 
without  danger  of  oversetting.  On  the  other  hand,  if  the  bal- 
last is  too  heavy,  and  placed  too  low,  the  vessel  is  said  to  be 
too  stiff,  and  not  only  draws  so  much  water  as  to  impede  her 
velocity,  but  is  liable  to  have  her  masts  endangered  by  the 
shocks  which  result  from  the  suddenness  of  her  motions.  In 
regard  to  shape,  an  increase  of  the  width  of  a  ship,  increases 
her  stability,  but  at  the  same  time,  detracts  from  her  power,  as 
a  fast  sailer. 

Steam  Boats. — Experiments  on  the  propulsion  of  vessels  by 
steam,  were  made  in  Europe,  and  this  country,  at  different 
times  during  the  last  century,  but  the  first  successful  introduc- 
tion of  steam  navigation  on  a  large  scale,  was  made  in  America 
by  the  late  Mr  Fulton,  about  the  year  1807.  The  application 
of  the  steam  engine  to  navigation,  has  given  to  vessels  the  ad- 
vantage of  greater  speed  and  regularity^jn  the  performance  of 
their  passages,  without  interruption  from  the  changeable,  and 
often  adverse,  operation  of  the  elements.    In  the  action  of  the 


ARTS  OF  LOCOMOTION. 


221 


steam  engine,  as  in  that  of  rowing,  a  vessel  is  propelled  by  a 
succession  of  impulses,  which  act  against  the  inertia  of  the 
water. 

A  power  acting  within  a  boat,  whether  of  men,  of  horses,  or 
of  steam,  may  be  applied  to  the  water  in  various  ways.  Some 
of  the  principal  of  these,  are  the  following.  1.  A  system  of 
oars,  or  paddles  have  been  made  to  act  with  alternating  strokes, 
rising  out  of  water  at  the  end  of  each  stroke.  2.  An  alternat- 
ing paddle  has  been  contrived,  which  is  continually  immersed, 
and  which  folds  up  like  the  foot  of  a  w^ater  fowl,  during  the 
backward  stroke.  3.  It  has  been  proposed  to  drive  a  current 
of  air,  or  a  current  of  water,  out  at  the  stern  of  the  vessel.  4. 
Spiral  wheels  and  water  screws,  or  wheels  with  oblique  vanes, 
like  those  of  a  wind  mill,  have  been  made  to  turn  under  water, 
with  their  axes  parallel  to  the  keel  of  the  vessel.  5.  Oblique 
planes  acting  with  an  alternate,  instead  of  a  revolving  stroke, 
were  recommended  by  Bernoulli.  6.  Paddle  wheels.  These, 
from  their  simplicit}"  and  advantageous  mode  of  action,  have  in 
common  use  superseded  all  the  rest.  They  consist  of  paddles 
or  floatboards  attached  to  the  arms,  or  spokes,  of  a  wheel,  the 
axis  of  which  is  at  right  angles  with  the  keel.  Their  common 
place  is  on  the  sides  of  the  boat,  as  in  the  annexed  figure. 

Fig.  10. 


The  outline  of  the  floatboards,  or  paddles,  is  commonly  rec- 
tangular, though  Mr  Tredgold  recommends  that  their  outer  ex- 
tremity should  be  parabolic.  The  best  position  for  the  paddles 
is  in  a  plane  passing  through  the  axis  of  the  wheels,  but  ^vhh  this 
position,  they  strike  the  water  obliquely  in  entering,  and  lift  a 


222 


ARTS  OF  LOCOMOTION. 


considerable  quantity  on  quitting  it ;  both  of  which  motions  oc- 
casion loss  of  power.  Attempts  have  been  made  to  correct  this 
disadvantage  by  various  mechanical  arrangements,  in  which  the 
paddles  are  made  to  enter  and  leave  the  water  perpendicularly; 
but  want  of  simplicity,  and  objections  of  various  other  kinds,  have 
prevented  them  from  coming  into  use.  It  has  been  proposed 
to  fix  a  series  of  paddles  upon  longitudinal  chains,  passing 
round  wheels,  and  parallel  to  each  side  of  the  vessel.  By  this 
mode  a  number  of  perpendicular  paddles  would  act  upon  the 
water  at  once ;  but  it  will  be  seen,  that  as  no  more  of  these  pad- 
dles can  operate  usefully,  than  are  sufficient  to  put  the  water 
between  them  into  motion,  a  part  of  the  series  will  be  less  use- 
ful than  if  it  acted  upon  water  at  rest.  In  wheels  of  the  com- 
mon form,  it  is  advantageous  to  have  a  double  row  of  paddles, 
•one  outside  the  other,  and  so  placed  that  the  paddles  of  one  se- 
ries shall  be  opposite  the  intervals  of  the  other,  and  thus  enter 
the  water  successively,  and  in  different  places.  * 

Steam  boats  are  best  adapted  to  the  navigation  of  rivers  and 
straits,  or  sounds,  where  the  water  is  comparatively  smooth. 
They  are  also  used  in  the  open  sea,  but  the  violence  of  the 
waves  renders  the  action  of  the  paddle  wheels  irregular,  and  it 
is  found  difficult  for  them  to  carry  fuel  sufficient  to  supply  the 
engine  during  long  voyages.  These  obstacles,  however,  have 
been  in  part  surmounted,  and  steam  boats  now  ply  along  the 
coasts  both  of  America,  and  Europe.  The  steam  ship  Savan- 
nah, crossed  the  Atlantic,  in  1819,  and  was  21  days  from  land 
to  land,  during  18  of  which,  she  was  able  to  use  her  engine. 

DIVING  BELL. 

The  diving  bell  is  an  inverted  vessel,  containing  air,  and  used 
for  the  purpose  of  enabling  persons  to  descend  with  safety  to 
great  depths  under  water.    It  is  made  tight  at  the  top  and  sides, 

*  For  examinations  of  the  different  propelling  powers,  see  the  Edinburgh 
Encyclopedia,  article  '  Navigation  Inland, '  ascribed  to  Mr  Telford  ;  also 
Tredgold  on  the  Steam  Engine,  p.  309. 


ARTS  OF  LOCOMOTION. 


223 


but  is  entirely  open  at  bottom.  Its  principle  is  the  same  with 
that  of  a  gasometer,  and  may  be  familiarly  illustrated  by  im- 
mersing an  inverted  tumbler  in  a  vessel  of  water.  The  air 
cannot  escape  from  the  inside  of  the  vessel,  being  necessitated 
by  the  order  of  specific  gravities,  to  occupy  the  upper  part  of 
the  cavity. 

Diving  bells  appear  to  have  been  first  introduced  in  the  be- 
ginning of  the  sixteenth  century.  They  were  first  known  as 
objects  of  curiosity  only,  but  have  been  since  applied  to  the  re- 
covery of  valuable  articles  from  wrecks,  the  blasting  and  min- 
ing of  rocks  at  the  bottom  of  the  sea,  and  the  practice  of  sub- 
marine architecture.  They  may  be  made  of  almost  any  shape, 
but  the  common  form  has  been  that  of  a  bell,  or  hollow  cone^ 
made  of  wooden  staves,  and  strongly  bound  with  hoops,  having 
seats  for  the  occupants  on  the  inside.  It  is  suspended  with 
ropes  from  a  vessel  above,  and  is  ballasted  with  heavy  weights 
at  bottom,  which  serve  to  sink  it,  and  to  prevent  it  from  turning 
over.  More  recently  diving  bells  have  been  made  of  cast  iron. 
The  kind  of  bell  used  at  Howth,  near  Dublin,*  is  an  oblong 
iron  chest,  six  feet  long,  four  broad,  and  five  high,  thicker  at 
bottom  than  at  top,  and  weighing  four  tons.  It  has  a  seat  at 
each  end,  and  is  capable  of  holding  four  persons.  The  upper 
part  is  pierced  with  eight  or  ten  holes,  in  which  are  fixed  the 
same  number  of  strong  convex  glasses,  which  transmit  the  light. 
As  the  air  in  the  bell  becomes  contaminated  by  breathing,  it  is 
renewed  by  letting  down  barrels,  or  small  bells,  of  fresh  air, 
which  are  transferred  to  the  large  bell ;  or  else  by  keeping  up 
a  constant  supply  through  a  pipe,  by  means  of  a  forcing  pump, 
which  is  worked  by  men  at  the  surface. 

Persons  who  descend  in  diving  bells,  often  experience  a  pain 
in  the  ears,  and  a  sense  of  pressure,  occasioned  by  the  con- 
densation of  the  air  within  the  cavity  of  the  bell.  These  symp- 
toms gradually  pass  off,  or  habit  renders  the  body  indifferent 
to  them,  so  that  workmen  remain  under  water,  at  the  depth  of 

*  Edinburgh  Philosophical  Journal,  vol.  v.  p.  8. 


224 


ARTS  OF  LOCOMOTION. 


twenty  feet  or  more,  for  seven  or  eight  hours  in  a  day,  without 
detriment  to  the  health. 

Submarine  A^avigation. — A  machine  was  invented  during 
the  American  revolution,  by  Mr  Bushnell  of  Connecticut,  which 
was  capable  of  containing  a  person  in  safety  under  w^ater,  and 
of  being  governed  and  steered  in  any  direction  at  pleasure.  It 
is  described  *  as  being  a  hollow  vessel  of  a  spheroidal  form, 
composed  of  curved  pieces  of  oak,  fitted  together  and  bound 
with  iron  hoops,  the  seams  being  caulked  and  covered  with  tar 
to  render  them  tight.  A  top  or  head,  was  closely  fitted  to  the 
vessel,  and  served  the  purpose  of  a  door.  In  this  were  insert- 
ed several  strong  pieces  of  glass  to  admit  the  light.  The  ma- 
chine contained  air  enough  to  render  it  buoyant,  and  to  support 
respiration.  A  quantity  of  lead  was  attached  to  the  bottom  for 
ballast.  The  vessel  was  made  to  sink  by  admitting  water,  and 
to  rise,  by  detaching  a  part  of  the  leaden  ballast,  or  by  expel- 
ling water  with  a  forcing  pump.  It  was  propelled  horizontally, 
by  means  of  revolving  oars  placed  obliquely  like  the  sails  of  a 
windmill,  on  an  axis  which  entered  the  boat  through  a  tight 
collar,  or  water  joint,  and  was  turned  with  a  crank  within.  A 
rudder  was  also  employed  for  steering  the  vessel.  When  fresh 
air  was  required,  the  vessel  rose  to  the  surface  and  took  in  air 
through  apertures  at  the  top.  The  intention  of  this  machine 
was  to  convey  a  magazine  of  powder  under  ships  of  war  for  the 
purpose  of  blowing  them  up.  Several  experiments  were  made 
with  it,  which,  though  unsuccessful  in  their  object,  nevertheless 
proved  the  practicability  of  this  species  of  locomotion. 

The  late  Mr  Fulton,  made  various  experiments  on  subma- 
rine navigation,  in  a  boat  large  enough  to  contain  several  per- 
sons, furnished  with  masts  and  sails  so  as  to  be  capable  of  pro- 
ceeding at  the  surface  of  the  water,  and  also  of  plunging,  when 
required,  below  the  surface,  f  While  under  water,  its  motions 
were  governed  by  two  machines,  one  of  which  caused  it  to  ad- 
vance horizontally,  while  the  other  regulated  its  ascent  and 

*  Silliman's  Journal,  vol.  ii.  p.  94. 

t  See  Colden's  Life  of  Fulton,  8vo.  New  York,  1810. 


ARTS  OF  LOCOMOTION. 


226 


descent,  its  depth  below  the  surface  being  known  by  the  pres- 
sure on  a  barometer.  A  supply  of  fresh  air  was  carried  down 
in  the  boat,  condensed  into  a  strong  copper  globe,  by  which 
the  air  of  the  boat  was  replaced  when  it  became  unfit  for  res- 
piration. Mr  Fulton's  object  was  the  destruction  of  ships  of 
war,  by  bringing  underneath  them  an  explosive  engine  called  a 
torpedo. 

AEROSTATION. 

Balloon. — A  balloon  is  a  sphere,  or  bag,  formed  of  some 
light  material,  such  as  silk,  and  rendered  impervious  to  the  air, 
by  covering  it  with  elastic  varnish.  It  is  filled  with  a  gas- 
eous fluid,  lighter  than  the  surrounding  atmospheric  air,  and  has 
a  car  suspended  at  the  bottom.  If  the  specific  gravity  of  the 
whole  mass  is  less  than  that  of  an  equal  bulk  of  the  atmospheric 
air  which  surrounds  it,  the  balloon  will  ascend  into  the  atmos- 
phere, and  remain  suspended,  until  by  the  escape  of  its  gas,  or 
other  means,  it  becomes  heavier  than  the  surrounding  air,  when 
it  will  again  descend.  Balloons  were  invented  in  France,  by 
the  Montgolfiers,  about  1782.  Those  which  were  first  employ- 
ed by  them  were  filled  with  common  air  rarified  by  heat ;  but 
these  required  that  a  fire  should  be  constantly  kept  burning  be- 
neath them,  to  keep  them  afloat.  Hydrogen  gas  was  after- 
wards employed,  and  this  fluid,  being  permanently  about  four- 
teen times  less  dense  than  common  air,  is  undoubtedly  the  best 
material  for  aerostation.  Carburetted  hydrogen,  though  heav- 
ier than  hydrogen,  has  also  been  employed  of  late  on  account 
of  its  cheapness,  being  furnished  in  large  quantities  at  the  man- 
ufactories of  illuminating  gas. 

Balloons  are  made  by  sewing  together  pieces  of  silk,  the 
shape  of  which  corresponds  to  that  of  the  part  included  by  two 
meridians  of  the  artificial  globe.  They  have  also  been  made 
of  linen  and  of  paper.  They  are  varnished  with  a  solution  of 
elastic  gum,  to  render  them  tight.  A  net  work  is  thrown  over 
the  top  of  the  balloon,  to  which  is  attached  by  strings,  a  car  of 
29 


226 


ARTS  OF  LOCOMOTION. 


wicker  work,  nnderneath  the  balloon.  The  whole  is  kept 
down  by  a  sufficient  quantity  of  ballast,  and  ascends  into  the 
atmosphere  when  a  part  of  the  ballast  is  thrown  over.  It  is 
made  to  descend  again  by  suffering  a  part  of  the  gas  to  escape 
through  a  valve  provided  for  the  purpose. 

The  regulation  of  the  ascent  and  descent  of  balloons,  is  the 
extent  of  control,  which  has  been  hitherto  obtained  over  them. 
All  attempts  to  guide  or  propel  them,  by  means  of  wings,  sails, 
oars,  &:c.,  have  hitherto  failed,  and  the  machine  can  only  pro- 
ceed at  the  mercy  of  the  winds.  The  small  degree  of  buoy- 
ancy which  balloons  possess,  does  not  permit  them  to  carry  suf- 
ficient weight  of  material,  to  furnish  the  medium  of  an  adequate 
propelling  force.  By  taking  advantage,  however,  of  favorable 
winds,  voyages  have  been  made  in  them  to  the  distance  of 
300  miles  ;  and  persons  have  ascended  to  the  height  of  20,000 
feet  and  upwards.  The  velocity  of  balloons  varies  with  that  of 
the  wind,  but  has  in  some  instances  amounted  to  the  rate  of  70 
miles  an  hour.  * 

Parachute. — The  danger  which  attends  falling  from  great 
heights,  is  in  consequence  of  the  continual  acceleration  of  veloci- 
ty which  falling  bodies  experience.  When,  however,  tlie  re- 
sistance of  the  atmosphere  becomes  equal  to  the  force  of  gravi- 
ty, the  motion  is  no  longer  accelerated,  but  becomes  uniform. 
A  parachute  is  an  appendage  to  a  balloon,  formed  somewhat 
like  an  umbrella,  and  is  designed  to  break  the  force  of  a  fall, 
by  means  of  the  large  surface  which  it  opposes  in  its  progress, 
to  the  atmosphere.  It  is  made  of  silk,  or  canvass,  and  is  plac- 
ed underneath  the  balloon,  having  the  car  suspended  from  it 
by  cords.  When  the  balloon  is  at  any  height  in  the  air,  the 
parachute  may  be  detached  from  it,  and  will  immediately  fall 
with  the  car  to  the  ground.  But  the  resistance  of  so  large  a 
surface  to  the  atmosphere,  causes  the  fall  to  be  gradual  and  easy, 

*  M.  Gay-Lussac,  on  the  6th  of  September,  1804,  ascended  23,100  feet 
above  Paris.  M.  Garnerin,  September  2lst,  1827,  passed  in  seven  hours  and 
a  half,  from  Paris  to  Mount  Tonnere,  a  distance  of  300  miles.  This  voyage 
was  performed  in  the  night,  and  during  a  storm. 


ARTS  OF  LOCOMOTION. 


227 


so  that  a  person  may  descend  with  a  parachute  in  safety  from 
the  t^reatest  heights.  The  size  of  the  parachute  employed  by 
J\I.  Garnerin,  and  with  which  he  descended  from  a  height  of 
2000  feet,  at  Paris,  in  1797,  was  25  feet  in  diameter.  The 
parachute  was  folded  up  at  the  beginning  of  the  fall,  but  soon 
expanded  itself  by  the  resistance  of  the  atmosphere.  The  on- 
ly inconvenience  which  was  experienced,  arose  from  a  violent 
oscillating  motion. 


Brewster's  Edition  of  Ferguson's  Lectures  on  Mechanics,  «fcc.  2 
vols,  8vo.  1823; — Anstice  on  Wheel  Carriages; — Edgeworth  on 
Roads  and  Carriages,  8vo. ; — Deparcieux  sur  le  tirage  des  chevaux, 
in  the  Mem.  de  VAcad.  Paris,  1760 ; — Young's  Lectures  on  Natural 
Philosophy; — McAdam,  on  Roads,  8vo.  1823; — Tredgold,  on  Rail 
Roads,  8vo.  1825; — Wood,  on  Rail  Roads,  8vo.l825  ; — Strickland's 
Reports  on  Canals,  Railroads,  &c.,  oblong  fol.  Philad.  1820 ; — Article 
Canal,  in  Rees's  Cyclopedia,  written  by  Mr  J.  Farey  ; — Articles  Navi- 
gation Inland,  Railway,  Bridges,  Aeronautics,  &c.,  in  the  Edinburgh 
Encyclopedia; — Chapman  on  Canal  Navigation, 4to.  1797 ; — Fulton 
on  Canal  Navigation,  4to.  1796; — Smeaton's  Reports,  3  vols,  8vo. 
1812  ; — Pront,  Architecture  Hydraulique,  2  torn.  4to.  1790 ; — Belidor, 
Architecture  Hydraulique,  4  torn.  4to.  1750; — De  Cess  art,  Travaux 
Hydraidiques,  2  torn.  4to.  1808 ; — Reports  to  the  House  of  Commons 
on  Roads,  Steam  Boats,  &,c.,  1822,  &c. ; — Article  Seamanship,  in 
the  Encyclopedia  Brittannica,  by  Prof.  Robison ; — Dupin,  Voyage 
dans  la  Grand  BretangCy  6  vols,  8vo.  with  plates,  fol.  1825. 


CHAPTER  XI. 


ELEMENTS  OF  MACHINERY. 

Machines. — By  a  machine,  may  be  understood  a  combina- 
tion of  mechanical  powers,  adapted  to  vary  the  direction,  appli- 
cation, and  intensity,  of  a  moving  force,  so  as  to  produce  a 
given  result.  The  advantage  which  machines  possess  over 
common  manual  labor,  is  generally  that  of  increasing  or  im- 
proving the  product  of  an  operation.  This  end  they  accom- 
plish, by  enabling  us  to  apply  a  common  force  more  advanta- 
geously, or  to  employ  the  most  powerful  force  derived  from 
natural  agents,  with  precision  and  efficacy.  By  the  aid  of 
machinery  any  number  of  instruments,  or  operative  parts,  may 
be  made  to  move  in  concert,  in  every  possible  direction,  with 
any  degree  of  velocity  ;  and  to  reciprocate  with  each  other  in 
perfect  harmony,  so  that  complex  operations  are  performed  by 
them,  with  a  precision  which  often  exceeds  the  skill  of  the 
most  expert  artist. 

Motion. — The  motion  which  takes  place  in  machines  is  for 
the  most  part,  either  rotary  or  reciprocating.  A  rotary  motion 
is  that  in  which  the  moving  parts  revolve  round  an  axis,  as  in  a 
wheel,  a  crank,  or  a  fly.  A  reciprocating  or  alternate  motion,  is 
that  in  which  a  body  retraces  its  own  path,  or  moves  alter- 
nately backward  and  forward  in  the  same  track,  which  may  be 
curved,  as  in  the  beam  of  a  steam  engine,  or  rectilinear,  as  in 
the  piston.  Most  compound  machines  possess  both  these 
kinds  of  motion,  or  varieties  derived  from  them  ;  and  the  dif- 
ferent ways  of  producing  and  communicating  them  in  the  re- 
quisite times  and  places,  constitute  a  principal  subject  of  atten- 
tion with  machinists. 


ELEMENTS  OF  MACHINERY.  229 


ROTARY,  OR  CIRCULAR  MOTION. 


When  it  is  intendeil  that  one  wheel  or  axle  shall  propel 
another,  various  contrivances  are  adopted  to  connect  the  pro- 
pelling part  with  that  which  is  to  be  moved.  The  mode  of 
connexion  is  varied  according  to  the  distance,  the  relative  ve- 
locity required,  and  the  direction  in  which  motion  is  to  be 
communicated. 

Band  Wheels, — If  two  wheels  be  connected  by  a  belt,  or 
band,  passing  round  their  circumferences,  they  will  move  simulta- 
neously, provided  the  friction  of  the  band  is  sufficient  to  prevent 
it  from  slipping.  When  a  round  cord  is  used,  any  degree  of 
friction  may  be  produced  by  receiving  the  cord  in  a  sharp 
groove,  at  the  edge  of  the  wheel.  But  the  stiffiiess  of  cords 
forms  in  many  cases,  an  objection  to  their  use.  When  a  strap, 
or  flat  band,  is  used,  its  friction  may  be  increased 
by  increasing  its  width.  The  surface  at  the  cir- 
cumference of  a  wheel,  or  drum,  which  carries  a 
flat  band,  should  not  be  exactly  cylindrical,  but  a 
little  convex,  in  which  case  if  the  band  inclines  to 
slip  off  at  either  side,  it  returns  again  by  the  tight- 
ening of  its  inner  edge,  as  maybe  seen  in  a  turner's 
lathe.  When  wheels  are  connected  in  the  shortest 
manner  by  a  band,  as  in  Fig.  1,  they  move  in  the 
same  direction.  If  the  band  be  crossed,  as  in 
Fig.  2,  they  will  move  in  opposite  directions. 
Wheels,  whose  axes  are  situated  in  different  planes, 
may  turn  each  other  if  the  band  be  sufficiently  long. 
If  no  slipping  were  to  take  place  in  the  band, 
wheels  of  equal  size  would  move  with  equal  velo- 
city, and  those  of  different  sizes,  with  velocities  in- 
versely proportionate  to  their  respective  circumfer- 
ences. But  since  the  band  is  liable  to  yield  or  slide 
somewhat  during  the  revolution,  the  velocity  of  the 
driven  wheel  is  commonly  a  little  less  in  proportion, 
than  that  of  the  wheel  which  drives  it. 


230 


ELEMENTS  OF  MACHINERY. 


Rag  Wheels. — Where  it  is  necessary  that  the  velocities 
should  be  exactly  proportionate,  also  where  great  resistance  is 
to  be  overcome,  chains  of  various  kinds  are  substituted,  bypass- 
ing them  round  wheels,  in  the  place  of  btlts  and  ropes.  These 
chains  lay  hold  upon  pins,  or  enter  into  notches  on  the  circum- 
ference of  the  wheels,  so  as  to  jp^^-,  3, 
cause  them  to  turn  simultane- 
ously. Such  wheels  are  de- 
nominated rag  wheels,  and 
have  a  uniform  relative  velo- 
city. Fig.3.  They  are  used 
in  locomotive  steam  engines,  chain  water  wheels,  &;c. 

Toothed  Wheels. — Toothed  wheels  afford  a  more  regular 
and  effectual  mode  of  communicating  rotary  motion,  than  any 
other  kind  of  connecting  mechanism.  They  move  of  necessity 
in  opposite  directions,  and  their  relative  velocity  is  inversely 
proportionate  to  their  number  of  teeth.  Thus  if  a  wheel  hav- 
ing forty  teeth  drives  another  of  ten  teeth,  the  second  will  make 
four  revolutions  while  the  first  makes  one.  The  connexion  of 
one  toothed  wheel  with  another,  is  called  gear  or  gearing,  and 
when  both  wheels  with  their  teeth  are  in  the  direction  of  the 
same  plane,  it  is  called  spur  gearing.  It  is  desirable  in  tooth- 
ed wheels,  as  far  as  possible,  to  diminish  friction,  and  to  pro- 
duce uniformity  of  force  and  motion.  A  uniform  motion  may 
be  produced,  if  the  form  of  the  acting  face  of  the  teeth  be  a 
curve  of  the  epicycloidal  kind  ;  the  outline  of  the  teeth  of  one 
wheel  being  the  curve  which  would  be  described  by  the  revo- 
lution of  a  curve  upon  a  given  circle,  while  the  outline  of  the 
teeth  of  the  other  wheel,  is  described  by  the  same  curve  rolling 
within  the  circle.  It  may  also  be  produced,  if  the  teeth  of  one 
wheel  be  straight,  circular,  or  of  any  regular  figure  whatever ; 
provided  the  teeth  of  the  other  wheel,  be  of  a  figure  compound- 
ed of  that  figure  and  of  an  epicycloid. 

*  For  investigations  relating  to  the  teeth  of  wheels,  see  Camus  on  the  Teeth 
of  Wheels,  translated,  London,  8vo.  1806  ;— Buchanan  on  Mill  Work,  chap, 
i.  &,€. ;— Brewster's  Ferguson's  Lectures,  vol.  ii.  p.  119 ;— Gregory's  Mechan- 
ics, vol.  ii.  p.  451  ;— also  a  Treatise  by  Mr  Blake,  in  SilUman's  Journal,  vol. 
vii.  p.  86". 


ELEMENTS  OP  MACHINERY. 


231 


Of  two  wheels  which  are  unequal  in  size,  the  larger  is  called 
the  wheel,  and  the  smaller  the  pinion.  The  acting  portions  of 
the  wheel  are  called  teeth  ;  and  of  the  pinion,  more  commonly, 
leaves.  The  name  of  lanterns  is  given  to  pinions  with  two 
heads  connected  by  cylindrical  teeth,  or  trundles.  In  Fig.  4, 
the  line  joining  the  centres 
B  and  F  of  the  wheel  and  pin- 
ion, is  called  the  line  of  centres, 
and  when  this  line  is  divided 
into  two  parts,  ^F  A  and  BA, 
which  are  to  each  other  as  the 
number  of  leaves  in  the  pinion 
is  to  the  number  of  teeth  in  the 
wheel ;  B  A  is  called  the  primi- 
tive radius  *  of  the  wheel,  and 
F  A,  the  primitive  radius  of  the 
pinion  ;  while"  the  lines  or  dis- 
tances F  f  and  B  b,  are  called  the 
true  radii.  The  circles  X  AX 
and  R  A  R  are  called  the  prim- 
itive circumferences,  and  by  workmen,  the  pitch  lines. 

Friction,  to  a  certain  extent,  cannot  be  avoided,  in  teeth  of 
the  common  kind,  whose  acting  faces  are  at  right  angles  w^ith 
the  plane  of  the  w^heels  to  which  they  belong.  It  may,  howev- 
er, be  much  diminished,  by  making  the  teeth  as  small  and  as 
numerous,  as  is  consistent  with  their  strength ;  for  the  quantity 
of  friction  necessarily  increases  with  the  distance  of  the  point 
of  contact  from  the  line  of  centres. 

Spiral  Gear. — In  common  cases,  the  teeth  of  wheels  are 
cut  across  the  circumference,  in  a  direction  parallel  to  the  axis. 
In  the  spiral  gear,  now  much  used  in  cotton  mills,  in  this  coun- 
try, the  teeth  are  cut  obliquely,  so  that  if  continued  they  would 
pass  round  the  axis  like  the  threads  of  a  screw.  In  conse- 
quence of  this  disposition,  the  teeth  come  in  contact  only  in  the 


Fig.  4. 


*  Called  the  proportional  radius  by  Buchanan. 


ELEMENTS  OF  MACHINERY. 


lineof  centres,  and  thus  operate  without  friction.  Fig.  5. 
Fig.  5.  The  action  of  these  wheels,  it  is  true,  is 
compounded  of  two  forces,  one  of  which  acts  in 
the  direction  of  the  plane  of  the  wheel,  and  the 
other  in  the  direction  of  its  axis.  The  latter 
force  occasions  a  degree  of  friction,  which  being 
expended  at  the  end  of  the  axle,  may  be  regard- 
ed as  inconsiderable.  The  remaining  force 
goes  to  produce  rotary  motion. 

The  spiral  gearing  has  been  apphed  to  clockwork,  and  has 
the  peculiarity  that  it  admits  of  a  smaller  pinion  than  any  other 
gearing.  Thus,  if  a  very  small  cylinder  have  a  spiral  groove 
so  cut  in  it  as  to  extend  once  round  its  circumference,  it  will 
perform  one  revolution  for  every  tooth  of  the  wheel  which 
drives  it.  The  groove  may  be  cut  indefinitely  near  to  the 
centre  of  the  pinion  or  cylinder,  without  weakening  it  so  much 
as  w^ould  happen  in  other  forms  of  the  pinion.  ^ 

Bevel  Gear. — When  wheels  are  not  situated  in  the  same 
plane,  but  form  an  angle  with  each  other,  the  spur  gearing  al- 
ready described,  is  changed  for  teeth  of  a  different  description. 
In  this  case,  the  hevel  gearing  is  commonly  employed,  consist- 
ing of  wheels  which  are  frusta  of  cones,  having  their  teeth  cut 
obliquely,  and  converging  toward  the  point  where  the  apex  of 
the  cone  would  be  situated.  According  as  the  relative  magni- 
tude of  the  wheels  varies,  the  angle  of  the  pig^ 
bevel  must  be  different,  so  that  the  velocities 
of  the  wheels  may  be  in  the  same  proportion 
at  both  ends  of  their  oblique  sides  or  faces. 
For  this  purpose  the  faces  of  all  the  teeth 
must  be  directed  to  the  point  where  the  axes 
of  the  two  wheels  would  meet.  The  bevel 
gearing  is  shown  in  Fig  6,  and  Fig.  12. 

*  The  spiral  gear  has  been  used  at  Waltham,  Mass.  and  elsewhere,  for  about 
fifteen  years,  and  is  commonly  considered  here  as  the  invention  of  Mr 
White.  Something  analogous  to  it,  under  the  name  of  Inclined  Plane  Wheels, 
was  published  in  London,  by  Mr  T.  Sheldrake,  in  1811. 


ELEMENTS  OF  MACHINERY. 


233 


Crown  Wheel, — Circular  motion  is  also  communicated  at 
right  angles,  by  means  of  teeth  or  cogs,  situated  parallel 
to  the  axis  of  the  wheel.     Wheels   thus  7^ 
formed  are  denominated  crown,  or  contrate 
wheels.    They  act  either  upon  a  common 
pinion,  or  upon  a  lantern.    The  crown  wheel 
is  represented  in  Fig.  7.    It  is  less  in  use 
than  the  bevel  gear  before  described,  having 
more  friction. 

Universal  Joint. — The  contrivance  called  Hooke's  universal 
joint,  is  sometimes  used  instead  of  wheels,  to  communicate 
circular  motion  in  an  oblique  direction.  It  consists  of  two 
shafts,  or  axes,  each  terminating  in  a  semicircle,  and  connected 
together  by  means  of  a  cross,  upon  which  each  semicircle  is 
hinged.     Fig.  8.     It  is  obvious  j^^^  g 

that  when  one  shaft  is  turned,  the 
other  must  revolve  hkewise;  and 
this  will  be  the  case  whenever  the 
angle  by  which  one  shaft  deviates 
from  the  direction  of  the  other,  does 
not  exceed  40  degrees.  By  means 
of  a  double  universal  joint,  circular 
motion  may  be  communicated  at  an 
angle  of  from  50  to  90  degrees. 

Perpetual  Screw. — The  perpetual  or  endless  screw,  some- 
times called  tuorm  by  mechanics,  is  made  use  of  to  convey 
circular  motion  from  an  axle  to  a  toothed  wheel,  situated  in 
the  direction  of  the  same  plane  with  the  axle.  The  relative 
velocity  of  a  wheel  driven  by  a  screw  is  Fig.  9. 

very  slow,  for  if  the  screw  have  only  a 
single  thread,  the  wheel  will  advance  the 
breadth  of  one  tooth  only  for  each  revo- 
lution of  the  screw.  This  mechanism  is 
of  great  use  in  producing  an  equable 
slow  motion  in  machinery,  and  also  in 
increasing  mechanical  power.  Fig.  9. 
30 


234 


ELEMENTS  OF  MACHINERY. 


The  motion  may  be  reversed,  or  conveyed  from  the  wheel  to 
the  screw  if  the  obliquity  of  the  threads  be  sufficiently  increas- 
ed.   A  spiral  wheel  and  a  toothed  wheel  may       Fig.  10. 
be  made  to  turn  with  equal  velocity,  or  any  ^ 
desired  proportion  of  velocity,  by  the  construc- 
tion represented  in  Fig.  10.    A  is  a  wheel 
seen  edgeways,  its  axis  being  B  C.    Its  cir- 
cumference is  furnished  with   spiral  ridges, 
which  as  the  wheel  turns,  cause  the  pinion  D 
to  revolve  in  the  plane  of  the  axis  B  C. 

Brush  Wheels. — In  light  machinery,  wheels  sometimes  turn 
each  other  by  means  of  bristles  or  brushes  fixed  to  their  cir- 
cumference. They  may  also  communicate  circular  motion  by 
friction  only.  In  this  case  the  surface  brought  in  contact  is 
formed  of  the  end  grain  of  wood,  or  it  is  covered  with  leather 
or  some  other  elastic  substance,  and  the  two  wheels  are  pressed 
together  to  increase  the  friction. 

Ratchet  Wheel. — The  ratchet  or  detent  wheel,  is  intended 
to  prevent  motion  in  one  direction,  while  it  permits  it  in  another. 
For  this  purpose  the  teeth  are  cut  with  their  faces  inclining  in 


one  direction,  and  a  small  lever  or  catch,  is  so 


Fig.  11. 


placed  as  to  enter  the  indentations  and  stop 
the  wheel  if  it  turns  backward,  but  slides  over 
the  teeth  without  obstructing  them,  if  it  moves 
forward.  Fig.  11.  Ratchet  wheels  are  gen- 
erally employed  to  prevent  a  weight  raised  by 
a  machine  from  descending,  and  to  obviate 
other  retrograde  movements. 

Distant  Rotary  Motion. — When  it  is  required  to  transmit 
circular  motion  to  a  distance,  for  example  from  one  extremity 
or  story  of  a  building  to  an- 


other, various  methods  are 
employed.  The  most  com- 
mon is  by  band  wheels,  or 
drums  connected  by  leather 
belts  of  the  requisite  length. 
This  mode  is  considered  most 


Fig.  12. 


ELEMENTS  OF  MACHINERY. 


235 


economical.  When  a  precise  velocity  is  required,  a  rolling 
shaft  geared  at  both  ends,  as  in  Fig.  12,  is  to  be  preferred. 
A  double  crank  having  its  Fig.  13. 

two  parts  at  right  angles 
with  each  other,  and  con- 
nected with  a  similar  crank 
by  stiff  rods  or  bars,  answers 
the  same  purpose.  Fig  13. 
If  triple  cranks  are  used,  cords  will  serve  instead  of  bars  for 
connexion,  because  in  this  case,  some  part  of  the  first  crank 
will  always  be  in  a  situation  to  draw  the  second,  and  a  rigid 
medium  will  not  be  necessary. 

Change  of  Velocity. — It  is  sometimes  necessary  that  a  ma- 
chine should  be  propelled  with  a  velocity  which  is  not  equable, 
but  which  continually  changes  in  a  given  ratio.  This  happens 
in  cotton  mills  where  it  is  necessary  that  the  speed  of  certain 
parts  of  the  machinery  should  continually  decrease  from  the 
beginning  to  the  end  of  an  operation.  To  effect  this  object 
two  cones,  or  conical  drums,  are  used  having  their  larger  diam- 
eters in  opposite  directions.  They  are  connected  by  a  belt, 
which  is  so  governed  by  proper  mechanism,        pig^  14. 

that  it  is  gradually  moved  from  one  extremity       fl   II 

of  the  cones  to  the  other,  thus  acting  upon  / 
circles  of  different  diameter,  causing  a  con-  i — 
tinual  change  of  velocity  in  the  driven  cone,  / 
with  relation  to  that  which  drives  it.  Fig.  14.  (T 

A  change  of  speed  is  also  effected  by  a  decreasing  series  of 
toothed  wheels  placed  in  the  order  of  their  size  upon  a  com- 
mon axis,  and  fixed.  A  corresponding  series  in  an  inverted 
order  are  placed  upon  another  axis,  and  not  fixed,  but  capable 
of  revolving  about  the  axis,  like  loose  pullies.  The  axis  of 
this  second  series,  is  made  hollow  and  contains  a  moveable 
rod  which  has  a  tooth  projecting  through  a  longitudinal  slit  in 
one  side  of  the  axis.  This  tooth  serves  to  lock  any  one  of  the 
wheels  by  entering  a  notch  cut  for  its  reception.    Only  one 


236 


ELEMENTS  OF  MACHINERY. 


wheel,  however,  can  be  locked  at  a  time,  the  Fig.  15. 
others  remaining  loose,  so  that  the  axis  will  re- 
volve with  a  velocity  which  is  due  to  the  rela- 
tive size  of  the  particular  wheel  which  is  locked, 
and  of  the  wheel  which  drives  it.  By  succes- 
sively locking  the  different  wheels  an  in- 
crease or  decrease  of  speed  is  obtained.  * 
Fig.  15. 

Another  mode  of  changing  speed  is  produced  by  a  large 
and  small  wheel  placed  at  right  angles  with 
each  other,  and  acting  by  friction  only.  The 
edge  of  the  smaller  wheel  is  kept  in  close 
contact  with  the  disc  or  flat  surface  of  the 
larger  wheel,  so  that  the  smaller  wheel  will 
revolve  faster  or  slower,  according  to  the  dis- 
tance at  which  it  is  kept  from  the  centre  of 
the  larger  wheel.  The  distance  may  be  varied 
at  pleasure.    Fig.  16. 

It  is  sometimes  requisite  that  a  wheel  or  axis  should  move 
with  different  velocity  in  different  parts  of  a  single  revolution, 
as  in  orreries,  &ic.  This  may  be 
effected  by  an  eccentric  crown 
wheel  acting  on  a  long  pinion  as  in 
Fig.  17.  It  may  also  be  accom- 
plished in  a  different  way  by  a  cone 
furnished  with  a  spiral  line  of  teeth, 
acting  on  another  cone,  the  position 
of  which  is  reversed. 

Fusee, — In  the  preceding  arrangements  for  changing  velocity, 
there  is  a  corresponding  change  of  force,  which  is  in  an  inverse 
ratio  to  the  change  of  velocity.  They  may  therefore  be  em- 
ployed for  varying  force,  as  well  as  speed.  The  fusee  of  a 
common  watch  is  a  contrivance  adapted  to  this  purpose. 
When  a  watch  is  recently  wound  up,  the  spring  which  propels 


Fis:  17. 


'A  mechanism  of  this  kind  is  nsed  in  tlie  Cotton  Factory  at  Newton,  Mass. 
and  there  is  one  nearly  similar  in  Bramah's  planin«;  machine. 


ELEMENTS  OF  MACHINERY. 


337 


it  is  in  th^  state  of  greatest  tension.  As  this  spring  relaxes  or 
uncoils  itself,  its  power  decreases,  and  in  order  to  correct  tliis 
inequality,  the  chain  through  which  it  acts,  is  wound  upon  a 
spiral  fusee.  The  fusee  B  is  an  axis  surrounded  by  a  spiral 
groove,  the  distance  of  the  groove  from  the  axis  being  made 
to  increase  gradually  from  the  top  to  the  bottom,  so  that  in 
proportion  as  the  force  of  the  spring  is  diminished,  it  may  act 
on  a  longer  lever.  The  general  outline  of  the  fusee  must  be 
nearly  such,  that  its  thickness  at  any  part  may  diminish  in  the 
same  proportion  as  it  becomes  more  distant  from  the  point  at 


which  the  force  would 
cease  altogether,  the 
general  curve  being 
that  of  a  hyperbola ; 
but  the  workmen  have 
in  general,  no  other  rule 


than  that  of  habitual  estimation 


Fig.  18. 


ALTERNATE  OR  RECIPROCATING  MOTION. 

This  name  is  applied  to  movements  which  take  place  con- 
tinually backwards  and  forwards  in  the  same  patli.  An  alter- 
nate motion  may  take  place  about  a  centre,  in  which  case  the 
moving  parts  will  describe  arcs  of  circles,  as  in  a  tilt  hammer, 
or  the  beam  of  a  steam  engine;  or  it  may  be  confined  by 
guides  so  as  to  pursue  a  rectilinear  path,  as  in  the  saw  of  a  saw^- 
mill.  In  most  complex  machines,  both  rotary  and  reciprocat- 
ing motions  occur,  and  these  motions  are  converted  into  each 
other  by  any  of  the  following  contrivances. 

Cams. — If  the  axis  of  a  wheel  be  situated  in  any  other 
point  than  its  centre,  the  wheel  thus  rendered  eccentric,  may 
produce  by  its  revolution  an  alternate  motion  in  any  part  ex- 
posed to  its  action.  Circles,  hearts,  ellipses,  parts  of  cir- 
cles, and  projecting  parts  of  various  forms,  are  made  to  pro- 
duce ahernate  motion,  by  continually  altering  the  distance  of 
some  moveable  part  of  the  machhie,  from  the  axis  about 


238 


ELEMENTS  OF  MACHINERY. 


which  they  revolve.  Such  projecting  parts  are  called  cam.* 
In  the  various  forms  which  are  shown  in  the  figures,  the  part 
removed  hy  the  cam  is  supposed  to  return  by  its  own  gravity, 
or  by  some  other  power,  so  as  to  keep  up  the  alternate  motion. 
In  the  circular  eccentric  cam,  or  wheel,  Fig.  19,  the  sliding  or 
reciprocating  part  AB,  will  ascend  and  descend  with  an  easy 
motion,  being  never  at  rest  unless  at  the  instant  of  changing  its 
direction.  Eccentric  wheels  if  surrounded  by  a  hoop,  as  at 
H,  in  PI.  IX,  perform  the  same  office  as  cranks.  In  the 
semicircular  cam,  Fig.  20,  the  reciprocating  part  will  remain 
at  rest  on  the  periphery  of  the  cam  during  half  the  revolution, 
but  in  the  remaining  half  it  will  approach  the  axis  and  return. 
In  the  quadrant  cam.  Fig.  21,  the  reciprocating  part  will  re- 
main at  rest  on  the  periphery  during  the  first  quarter  of  the 
revolution  ;  during  the  second  it  will  descend  to  the  axis ;  dur- 
ing the  third  it  will  be  at  rest  upon  the  axis,  and  during  the 
fourth  it  will  return  to  its  original  situation.  The  narrow  cam, 
Fig.  22,  causes  the  reciprocating  part  to  rise  and  fall  in  one 
half  the  revolution,  and  to  remain  at  rest  on  the  axis  during 
the  other  half.  In  these  figures  the  angles  of  the  cams  are 
made  sharp,  for  the  sake  of  demonstration,  but  in  practice  they 
are  generally  rounded,  to  produce  more  gradual  changes 
of  motion.  The  elliptical  cam  Fig.  23,  causes  two  alter- 
nate movements  for  each  revolution ;  and  the  triple  cam  in 


Fig.  19. 

A  • 


Fig.  20. 
A 


O  = 


Fig.  21. 
A 


Fig.  22. 
A 


Fig.  23. 
A 


*  This  word  is  spelt  cam,  camm,  and  camb,  by  different  writers.  In  French 
eamc.  Borgnis. 


ELEMENTS  OF  MACHINERY. 


239 


Fig.  24,  applied  to  a  tilt,  or  trip  ham-  Fig.  24. 

mer,  causes  three  strokes  for  one  rev- 
olution. In  this  case  the  cams  are 
called  wipers,  and  it  is  common  to  ac- 
celerate the  reciprocal  motion,  by  add- 
ing to  the  action  of  gravitation,  the 
elastic  force  of  a  spring,  or  by  the  recoil 
of  the  handle  from  a  fixed  obstacle.  A  cam  in  the  form  of  a 
heart,  called  a  heart  wheel,  is  much  used  in  cotton  mills  to 
cause  a  regular  ascent  and  descent  of  the  rail  on  which  the 
spindles  are  situated.* 

When  an  easy  motion  is  desired,  as  in  most  large  machinery, 
the  acting  outline  of  the  cam  should  be  curved  ;  but  to  produce 
a  sudden  stroke  it  should  be  straight.  The  number  of  cams 
may  be  indefinitely  multiplied,  if  a  rapid,  or  vibrating  move- 
ment is  required.  This  is  in  effect  done,  when  the  teeth  of  a 
wheel  act  upon  a  spring  or  weight,  as  in  a  watchman's  rattle, 
or  in  the  feeder  of  a  grist  mill. 

Crank. — The  common  crank  affords  one  of  the  simplest  and 
most  useful  methods  for  changing  circular  into  alternate 
motion,  and  vice  versa.  The  single  crank.  Fig.  25,  can  only 
be  used  upon  the  end  of  an  axis.  The  bell  crank.  Fig.  26,  may 
be  used  in  any  part  of  an  axis.    The  double  crank.  Fig.  27, 


Fig.  25. 


Fig.  26. 


Fig.  27. 


n 


*  For  an  investigation  of  the  curves  proper  for  different  cams  and  wipers, 
see  Brewster's  edition  of  Ferguson's  Mechanics,  vol.  ii.  p.  126,  &c.  For 
producing  an  easy  and  uniform  motion,  spiral,  epicycloidal,  and  other  curves 
are  requisite  ;  but  for  abrupt,  forcible  motions,  such  as  occur  in  tilt  hammers, 
curves  of  equal  action  are  to  be  avoided. 


240 


ELEMENTS  OF  MACHINERY. 


produces  two  alternate  motions,  reciprocating  with  each  other. 
The  alternating  parts  in  all  these  cases,  are  attached  to  the 
crank  by  connecting  rods,  or  by  some  of  the  kinds  of  mechan- 
ism hereafter  described.  The  motion  produced  by  cranks  is 
easy  and  gradual,  being  most  rapid  in  the  middle  of  the  stroke, 
and  gradually  retarded  toward  the  extremes ;  so  that  shocks 
and  jolts  in  the  moving  machinery  are  diminished,  or  w^holly 
prevented  by  their  use. 

Parallel  Motion. — The  name  of  parallel  motions  is  given  to 
those  arrangements  which  convert  circular  motion,  whether  con- 
tinued or  alternate,  into  alternate  rectilinear  motion,  and  vice  versa. 
Thus  the  beam  of  a  steam  engine  moves  in  circular  arcs,  while 
the  piston  moves  in  right  lines.  They  cannot,  therefore,  be  rig- 
idly connected  together,  without  doing  violence  to  the  machine, 
and  it  becomes  necessary  to  convert  one  movement  into  the  oth- 
er by  the  intervention  of  proper  mechanism.  A  moveable  par- 
allelogram is  principally  used  for  this  purpose,  and  will  be  de- 
scribed under  the  head  of  Steam  Engine.  A  similar  contrivance 
of  a  more  simple  form  is  shown  in  Fig.  28.  C  D  is  a  rod  mov- 
ing back  and  forwards  in  a  right  line.  Every  point  of  junction 
is  a  hinge  or  joint.  G  E  is  a  rod  moveable  about  E  as  a  cen- 
tre ;  and  F  H  a  rod  of  the  same  pig^  28. 
length,  moveable  about  F  as  a  .j 
centre ;  these  centres  being  equal- 
ly distant  from  the  path  of  C  D. 
G  H  is  a  bar  connecting  these  two 
rods  and  having  the  rod  C  D  at- 
tached by  a  joint  to  its  centre. 
When  the  whole  is  set  in  motion 
the  joint  G  will  describe  the  cir- 
cular arc  I K,  and  the  joint  H  will 
describe  the  circular  arc  G  H, 
while  the  joint  C  will  pursue  an 
intermediate,  or  rectilinear  course. 

Various  other  methods  are  practised  to  insure  a  rectilinear 
motion,  though  most  of  them  are  attended  with  greater  friction 


10 


<^  

--^K..  K 

F 

1 

ELEMENTS  OF  MACHINERY. 


241 


than  that  last  descri(3cd.  Thus  the  alternating  part  is  often 
confined  to  a  rectilinear  pnth  by  sliding  in  grooves,  guides,  or 
holes,   or    between  friction 


wheels  ;  a 


rod 


uniting  the  straight  and  circular 
motions,  as  in  the  last  instance. 
In  Carlwiighi's  steam  engine, 
the  straight  movement  of  the 
piston  is  secured  by  connecting 
it  with  two  cranks  acting  in 
opposition  to  each  other,  and 


having  their 


axles  geared  to- 


Ft>.  30. 


A  Tz 


gether  by  wheels,  as  repre- 
sented in  Fig.  29. 

The  connecting  rod  may  be  dispensed  with, 
if  a  transv^erse  groove,  or  slit,  be  cut  in  the  al- 
ternating part,  of  a  length  equal  to  the  diameter 
of  the  crank's  revolution  ;  as  in  Fig.  30.  The 
end  of  the  crank,  seen  at  a,  in  its  revolution 
traverses  the  whole  length  of  this  groove  which 
is  cut  in  the  crossbar  A  B,  while  the  main  bar 
C  D,  has  an  alternate  motion  in  the  straight 
path  to  which  it  is  confined.  As  the  space  of 
ascent  or  descent  of  the  bar  C  D  is  always 
equal  to  the  versed  sine  of  the  arc  described 
by  the  crank,  the  motion  of  the  bar  will  be  accelerated  towards 
the  middle  of  its  oscillations,  and  retarded  towards  the  ex- 
tremes. A  more  equal  motion  can  be  produced,  if  desired, 
by  substituting  for  the  straight  groove,  a  curviHnear  groove 
somewhat  like  the  figure  co  ;  but  this  method  is  attended  with 
much  friction  and  little  use. 

Sun  and  Planet  Wheel. — The  mechanism  which  bears  this 
name,  was  invented  by  Mr  Watt,  to  convert  reciprocating,  into 
circular  motion  in  the  Steam  Engine  ;  the  use  of  the  crank  for 
this  purpose  being  at  one  time  secured  by  patent  to  another 
31 


242 


ELEMENTS  OF  MACHINERY. 


individual.  In  Fig.  31,  a  view  is  given 
of  the  sun  and  planet  wheel.  A  is  the 
end  of  a  beam  having  a  reciprocating 
motion.  B  is  the  fly  wheel  of  the  en- 
gine, to  which  a  rotary  motion  is  to  be 
communicated.  Upon  the  axis  of  this 
fly  wheel  a  small  toothed  wheel  is  firmly 
fixed.  A  second  toothed  wheel  is  con- 
nected to  the  first,  by  a  loose  crank,  so 
as  to  be  capable  of  revolving  freely  about 
it.  This  second  wheel  is  firmly  fixed 
upon  the  end  of  a  connecting  rod,  which 
is  attached  by  a  joint  to  the  beam  of  the  engine.  The  two 
wheels  being  in  gear,  it  is  obvious  that  as  the  beam  A  rises  and 
falls,  the  second  wheel  with  the  assistance  of  the  fly,  will  re- 
volve quite  round  the  first,  and  if  the  number  of  teeth  be 
equal,  the  first,  or  sun  wheel,  must  perform  two  rotations  on  its 
axis,  while  the  second,  or  planet  wheel  revolves  once  round  it. 

Inclined  Wheel. — In  Fig.  32,  AB  is  a  wheel 
placed  obliquely  on  its  axis  C  D.  The  edge,  or 
periphery,  of  this  wheel  is  received  in  a  notch  at 
B,  of  a  sliding  bar  E  F.  As  the  wheel  revolves, 
the  bar  E  F  will  move  up  and  down,  once  dur- 
ing each  revolution.  This  reciprocal  motion 
may  be  indefinitely  varied  by  bending  the  edge 
of  the  wheel  into  different  curves  and  an- 
gles. 

Epicycloidal  Wheel. — A  very 
beautiful  method  of  converting 
circular  into  alternate  motion 
or  alternate  into  circular,  is 
shown  in  Fig.  33.  A  B  is  a 
fixed  ring,  or  wheel,  toothed  on 
its  inner  side.  C  is  a  toothed 
wheel  of  half  the  diameter  of 
the  ring,  revolving  about  the 
centre  of   the    ring.  While 


Fig.  33. 


ELEMENTS  OF  MACHINERY. 


243 


this  revolution  of  the  wheel  C  is  taking  place,  any  point  what- 
ever on  its  circumference  will  describe  a  straight  hne,  or  will 
pass  and  repass  through  a  diameter  of  the  circle  once  during 
each  revolution.  This  is  an  elegant  application  of  the  law  that 
if  a  circle  rolls  on  the  inside  of  another  of  twice  its  diameter, 
the  epicycloid  described  is  a  straight  line.  In  practice,  a  piston 
rod,  or  other  reciprocating  part,  may  be  attached  to  any  point 
on  the  circumference  of  the  wheel  C. 

Rack  and  Segment, — If  an  ahernating  motion  is  required, 
the  velocity  of  which  shall  be  always  equal,  a  rack  is  best 
adapted  to  produce  this 
effect.  In  Fig.  34,  A  B  is 
a  parallellogram  having  a 
rack  on  two  opposite  sides. 
C  is  a  half  wheel  toothed  on 
its  curved  side,  and  having 
its  centre  equally  distant  " 
from  the  two  racks.  It  is  obvious  from  inspection,  that  as  this 
half  wheel  revolves,  its  teeth  will  act  successively  upon  the 
two  racks,  and  cause  the  parallelogram  to  move  back  and 
forwards  with  a  uniform  motion.  The  change,  however,  from 
one  direction  to  the  other  will  be  nearly  instantaneous,  so  that 
this  plan  will  only  answer  in  machinery  which  is  very  light,  or 
of  slow  motion.  The  teeth  of  the  half  wheel  must  cover 
somewhat  less  than  half  a  circle,  that  they  may  not  become 
engaged  in  one  rack,  before  they  are  disengaged  from  the 
other. 

Rack  and  Pinion. — Another  contrivance  which  renders  the 
change  more  gradual,  is  re-  Fig.  35. 

presented  in  Fig.  35.  AB 
is  a  double  rack,  with  circular 
ends  fixed  to  a  beam,  capable 
of  moving  in  the  direction  of 
its  length.  The  rack  is  driv- 
en  by  a  pinion  P,  which  is 
capable  of  moving  up  and  down  in  a  groove  m  n,  cut  in  the 


I 


244 


ELEMENTS  OF  MACHINERY. 


cross-piece.  When  the  pinion  has  moved  the  rack  and  beam 
until  it  comes  to  the  end  B,  the  projecting  piece  a  meets  the 
spring  5,  and  the  rack  is  pressed  against  the  pinion.  The  pin- 
ion, then  working  in  the  circular  end  of  the  rack,  wiUbe  forced 
down  the  groove  m  n  until  it  works  in  the  lower  side  of  the 
rack,  and  moves  the  beam  back  in  the  opposite  direction ;  and 
in  this  way  the  motion  is  continued.  The  motion  of  the  pin- 
ion in  the  groove  will  be  diminished,  if  instead  of  a  double 
rack,  we  use  a  single  row  of  pins  which  are  parallel  to  the  axis 
of  the  pinion,  as  in  some  of  the  machines  called  mangles. 
Belt  and  Segment, — An  alternate   circular     Fig.  36. 


motion  is  converted  into  an  alternate  rectilinear 
motion,  in  fire  engines,  dressing  machines,  &;c. 
by  a  belt  or  chain  fastened  to  each  end  of  a  seg- 
ment, or  other  poition  of  a  wheel.  The  two 
belts  pass  by  each  other  and  are  attached  to  the 
opposite  ends  of  an  alternating  part.  When  the 
segment  turns  in  either  direction,  it  draws  after  it 
the  alternating  part  in  a  straight  line.    Fig.  36. 


Scapements. — In  clocks  and  watches  an  alternating  motion 
is  produced  in  the  pendulum  and  balance  wheel,  by  means  of 
the  mechanism  called  a  scapement.  In  the  more  simple  scape- 
ments two  teeth,  called  pallets,  are  made  to  vibrate  on  a  com- 
mon axis.  They  are  connected  with  a  toothed  wheel  in  such 
a  manner,  that  one  pallet  enters  between  the  teeth  of  the  wheel 
whenever  the  other  is  thrown  out  of  their  reach.  As  the  wheel 
revolves,  its  teeth  successively  impinge  against  one  or  the  other 
of  these  pallets,  and  by  causing  them  successively  to  escape, 
communicate  to  their  axis  a  vibrating,  or  alternate  motion. 
The  crutch  scapement.  Fig.  37,  is  an  arch  situated  in  the  same 
plane  with  the  scape  wheel,  and  parallel  to  the  plane  in  which 
the  pendulum  vibrates.  Its  pallets  successively  enter  and  escape 
from  the  teeth  of  the  wheels,  and  receive  from  it  a  vibrating 
motion.  In  the  old  or  common  watch  scapement.  Fig.  38,  a 
contrate,  or  crown  wheel  is  used  as  the  scape  wheel  and  the 
pallets  a  and  b  are  placed  upon  the  axis  of  the  balance  wheel, 


ELEMENTS  OF  MACHINERY. 


245 


SO  as  to  meet  the  teeth  successively  on  opposite  sides  of  the 
circumference  of  the  scape  wheel.    A  variety  of  other  more 
complicated  forms  of  the  scapement  are  also  in  use. 
Fig.  37.  Fig.  38. 


CONTINUED  RECTILINEAR  MOTION. 

A  long  continued  rectilinear  motion  is  not  to  be  produced  in 
the  parts  of  a  machine,  except  so  far  as  it  partakes  of  the  na- 
ture of  a  rotary  or  a  reciprocating  motion.  Thus  a  band 
passing  round  pullies  is  a  modification  of  rotary  motion,  and 
a  rack,  which  is  obliged  to  return  at  intervals,  has  a  reciprocating 
motion.  But  to  a  certain  extent,  the  motions  of  both  may  be 
regarded  as  continuously  rectilinear. 

Band. — If  it  is  required  to  produce  motion  in  a  right  line, 
which  shall  be  always  in  one  direction,  as  for  example  in  the 
feeding  parts  of  machines,  a  band  passing  round  pullies  or 
drums,  is  the  method  most  commonly  practised,  as  in  Fig.  1. 
If  a  precise  velocity  is  required,  the  band  may  be  perforated 
with  holes,  and  received  upon  short  pins  at  the  circumference 
of  the  wheels  ;  or  the  rag  wheel  and  chain  represented  in  Fig. 
3,  may  be  substituted. 


246 


ELEMENTS  OF  MACHINERY. 


Rack. — If  a  slow  rectilinear  motion  is  required  only  for  lim- 
ited times,  such  a  mechanism  may  be  used  as  will  permit  the 
moving  part  to  retrace  its  own  path  at  intervals,  and  regain  its 
original  situation.   Fig.  39.  Fig.  39. 

A  rack^  which  is  a  straight  ,  1 

bar  having  teeth  on  one  VljnjlJUVli;;i/]WJI^ 
side,  will  move  in  this  man- 
ner if  it  be  acted  on  by  a 
toothed  wheel,  or  by  a  per- 
petual screw.  If  the  thread 
of  a  perpetual  screw  be  formed  of  different  obliquity  in  different 
parts  of  its  circumference,  the  progressive  velocity  of  the  rack 
will  be  unequal,  instead  of  being  uniform.  And  if  a  part  of  the 
thread  be  in  a  plane  at  right  angles  with  the  axis  of  the  screw, 
the  rack  will  be  at  rest  while  that  part  of  the  screw  revolves  in 
contact  with  it. 

Universal  Lever. — A  rack  is  also  propelled  by  means  of  a 
catch,  or  dog,  connected  with  some  part  of  the  machine  which 
has  an  alternating  motion.  The  catch  causes  the  rack  to  ad- 
vance the  length  of  one  tooth,  at  each  stroke 
of  the  alternating  part.  The  universal  lever, 
sometimes  called  the  lever  of  La  Garousse, 
consists  of  a  bar  moving  upon  a  centre,  and 
having  a  moveable  catch  or  hook  attached  to 
each  side  and  acting  upon  the  oblique  teeth  of 
a  double  rack,  or  of  a  ratchet  wheel,  so  that 
the  alternating  motion  of  the  bar  causes  a 
progressive  motion  of  the  rack  or  wheel. 
Fig.  40. 

Screw. — A  common  screw  is  often  made  use  of  to  produce 
rectilinear  movements,  when  the  motion  is  intended  to  be  very 
slow,  or  when  great  power  is  required. 

Change  of  Direction. — A  change  from  one  path  or  direction 
to  another,  forming  an  angle  with  it,  may  be  produced  by  sev- 
eral of  the  mechanical  powers.  Thus  a  cord  passing  over  a 
pulley,  may  change  a  perpendicular  to  a  horizontal  motion,  as  at 


ELEMENTS  OF  MACHINERY. 


247 


P,  PI.  VIIIj  or  to  one  at  any  other  angle  required.  A  bent  lever 
like  that  represented  hy  y  z  in  PI.  IX,  produces  the  same  ef- 
fect, provided  the  moving  parts  are  confined,  by  guides,  to  their 
respective  paths.  An  inclined  plane  also,  if  it  moves  through 
the  length  of  one  side  of  a  parallelogram,  will  cause  another 
body  to  move  through  the  length  of  the  contiguous  side  at  right 
angles.  This  method,  however,  is  attended  with  much 
friction. 

Toggle  Joint. — The  knee  joint,  commonly  called  in  this 
country,  toggle  joint,  affords  a  very  useful  mode  of  converting 
velocity  into  power,  the  motion  produced  being  nearly  at  right 
angles  with  the  direction  of  the  force.  Its  operation  is  seen  in 
the  iron  joints  which  are  used  to  uphold  the  tops  of  chaises. 
It  is  also  introduced  into  various  modifications  Fig  41^ 
of  the  printing  press,  in  order  to  obtain  the 
greatest  power  at  the  moment  of  the  impres- 
sion. It  consists  of  two  rods  or  bars  connect- 
ed by  a  joint,  and  increases  rapidly  in  power 
as  the  two  rods  approach  to  the  direction  of 
a  straight  line.  *  In  Fig.  41,  a  moving  force 
applied  in  the  direction  C  D,  acts  with  great 
and  constantly  increasing  power  to  separate 
the  parts  A  and  B.  B 


OF  ENGAGING  AND  DISENGAGING  MACHINERY. 

In  many  cases,  particularly  where  numerous  machines  are 
propelled  by  a  common  power,  it  is  important  to  possess  the 
means  of  stopping  any  one  of  them  at  pleasure,  and  of  rest^^'ing 
its  motion,  without  interfering  with  the  rest.  To  produce  this 
effect,  a  great  variety  of  combinations  have  been  invented  un- 
der the  name  of  couplings.  These,  in  most  instances,  are 
sliding  boxes  which  move  longitudinally  upon  shafts  or  axles, 

*  An  investigation  of  the  power  of  this  combination,  is  given  by  the  late 
Professor  Fisher,  in  Silliman's  Journal,  vol.  iii.  p.  320. 


248 


ELEMENTS  OF  MACHINERY. 


and  serve  to  engage  or  lock  a  shaft  which  is  at  rest,  with  one 
which  is  in  motion ;  so  as  practically  to  convert  the  two  into 
one,  until  they  are  again  unlocked.  Couplings  are  sometimes 
provided  with  clutches,  or  glands,  which  are  projecting  teeth, 
intended  to  catch  on  other  teeth  or  levers,  and  thus  lock  the 
shafts  together.  Sometimes  they  have  bayonets,  or  pins 
adapted  to  enter  holes.  Sometimes  the  connexion  is  produc- 
ed by  friction  alone,  by  pressing  together  surfaces,  which  are 
either  flat,  or  conical.  Sometimes,  also,  wheels  are  thrown  in- 
to, and  out  of  gear,  which  is  done  by  causing  wheels  to  slide  in 
the  direction  of  their  axles,  or  in  some  cases  by  elevating  and 
depressing  the  axle  itself.  These  methods,  however,  are  diffi- 
cult and  unsafe.  The  live  and  dead  pulley,  afford  perhaps  the 
simplest  mode  of  engagement.  They  consist  of  two  parallel 
band-wheels  on  the  same  axle,  one  of  which  is  fast,  and  the 
other  loose,  or  capable  of  turning  without  the  axle.  The  band 
which  communicates  the  power,  is  placed  upon  the  loose  pul- 
ley, when  it  is  desired  to  stop  the  machine,  and  upon  the  fast 
pulley  when  it  is  intended  to  set  the  machine  in  motion.  A 
common  band  may  also  be  made  to  admit  of  motion  or  rest, 
according  as  it  is  rendered  tense  or  loose,  by  a  tightening 
wheel  pressed  against  its  side  by  a  lever. 


OF  EQUALIZING  MOTION. 

In  most  machines,  both  the  moving  force  and  the  resistance 
to  be  overcome,  are  liable  to  fluctuations  of  intensity  at  differ- 
ent times.  As  such  variations  influence  both  the  safety  and 
efficiency  of  machines,  it  is  necessary  to  provide  against  them, 
by  some  appendage,  which  shall  equalize  either  the  supply,  or 
the  distribution,  of  the  power. 

Governor. — The  name  of  governor  has  been  given  to  an 
ingenious  piece  of  mechanism,  which  has  been  introduced  to 
regulate  the  supply  of  steam  in  steam  engines,  and  of  water  in 
water  mills,  so  as  to  render  the  power  equable,  and  propor- 
tionate to  the  resistance  to  be  surmounted.    It  is  represented 


ELEMENTS  OP  MACHINERY. 


249 


in  Fig.  42.    A  B  and  A  C,  are  two  lev-  Fig.  42. 

ers  or  arms,  loaded  with  heavy  balls  at 
their  extremities  B  and  C,  and  suspended 
by  a  joint  at  A  upon  the  upper  extremity 
of  a  revolving  shaft  AD.  At  a,  is  a 
collar,  or  sliding  box,  connected  to  the 
levers  by  the  rods  a  h,  and  a  c,  with  joints 
at  their  extremities.  It  follows  that  when 
the  weights  B  and  C  diverge,  the  collar 
a  will  move  upward  on  the  shaft  A  D 
and  vice  versa.  The  governor  thus  con- 
structed, is  attached  to  some  revolving 
part  of  the  machine.  In  this  state  if  it  turns  too  rapidly,  the 
balls  B  and  C  move  outwards  by  their  centrifugal  force  and 
draw  upward  the  collar  a.  If,  on  the  other  hand,  the  speed 
diminishes,  the  balls  are  allowed  to  subside,  and  the  collar 
moves  down  upon  the  shaft.  In  the  steam  engine  the  collar 
has  a  circular  groove,  which  receives  the  end  of  a  forked  lever. 
As  the  collar  rises  and  falls,  this  lever  turns  upon  its  fulcrum, 
and  acts  remotely  to  open  or  close  a  throttle  valve  which  is 
placed  in  the  main  steam  pipe.  *  Whenever,  therefore,  the 
machine  moves  too  rapidly,  the  balls  recede  from  the  centre, 
the  collar  rises,  the  lever  moves  the  valve,  and  by  partially 
closing  the  pipe,  diminishes  the  quantity  of  steam  admitted 
from  the  boiler.  If  the  machine  moves  too  slowly,  the  reverse 
takes  place,  and  a  larger  amount  of  steam  is  admitted. 

In  water  wheels,  where  a  greater  power  is  necessary  to  con- 
trol the  supply  of  water,  the  governor  is  usually  connected  to 
the  sluice  gate  by  the  intervention  of  wheel  work.  This  may 
be  done  in  several  ways,  one  of  which  is  as  follows.  The 
lower  part  of  the  shaft  A  D,  carries  a  v^^heel  at  D  acting  upon 
two  others  beneath  it,  M  and  N.  While  the  machinery  moves 
with  its  proper  speed,  the  wheels  M  and  N  are  both  unlocked 
and  turn  loosely  round  their  axles,  and  the  gate  is  stationary. 
But  when  the  velocity  increases  or  diminishes,  the  collai'  a  ris- 

"^For  a  farther  account  of  the  governor,  see  the  article  Steam  Engine, 
32 


250 


t:lf.ments  of  macninerv. 


es  or  falls,  and  by  means  of  a  cam,  acts  upon  a  lever  above  it, 
or  upon  another  below  it,  so  as  to  lock  one  of  the  wheels  M  or 
N,  by  moving  a  clutch  situated  at  d.  These  wheels  being 
upon  a  common  axle,  are  capable  of  turning  this  axle  different 
ways.  When,  therefore,  one  wheel  is  locked  to  the  axle,  it 
acts  by  turning  a  perpetual  screw,  to  open  the  sluice  gate. 
When  the  other  is  locked,  the  axle  and  the  screw  turn  in  the 
opposite  direction,  and  partially  close  the  gate. 

The  foregoing  are  some  out  of  various  modes  in  w^hich  the 
governor  is  applied.  In  windmills  it  is  so  adapted  as  to  increase 
the  feeding,  or  supply  of  corn,  when  the  mill  goes  too  fast, 
and  also  to  vary  the  distance  of  the  millstones  from  each  other, 
if  necessary.  It  has  also  been  applied  to  clothe  and  unclothe 
the  sails  in  proportion  to  the  strength  of  the  wind. 

Fly  Wheel. — It  is  an  object  of  great  importance,  in  ma- 
chines, to  have  the  means  of  accumulating  power  when  the 
moving  force  is  in  excess,  and  of  expending  it  when  the  mov- 
ing force  operates  more  feebly,  or  the  resistance  increases. 
This  equalization  of  motion  is  obtained  by  what  is  called  ^fly, 
which  is  generally  made  in  the  form  of  a  heavy  wheel,  though 
sometimes  in  the  form  of  arms  or  crossbars  with  weights  at  their 
extremities.  A  fly  being  made  to  revolve  about  its  axis  keeps 
up  the  force  by  its  own  inertia,  and  disti'ibutes  it  in  all  parts  of 
its  revolution.  If  the  moving  power  slackens  it  impels  the 
machine  forward,  and  if  the  power  tends  to  move  the  machine 
too  fast,  it  keeps  it  back. 

Fly  wheels  are  capable  of  accumulating  power  to  a  great 
extent.  -A  small  force  continually  applied  to  the  surface  of  a 
heavy  revolving  wheel  will  accelerate  its  velocity  till  it  shall  be 
equal  to  that  of  a  musket  ball,  and  its  momentum  almost  irre- 
sistible. Fly  wheels,  to  act  with  the  greatest  efficacy,  should  be 
made  with  the  least  possible  surface,  that  their  motion  may  not 
be  impeded  by  the  resistance  of  the  air.  They  should  be 
made  of  iron,  and  if  they  cannot  be  cast  in  one  piece,  they 
should  be  firmly  hooped  or  bolted  together,  that  the  parts  may 
not  separate  by  their  centrifugal  force.    Fatal  accidents  have 


ELEMENTS  OF  MACHINERY. 


25i 


occurred  from  the  bursting  of  large  stones  used  as  flies,  or  as 
grindstones  in  cutlery  works,  their  velocity  and  centrifugal 
force  being  so  great  as  to  overcome  their  cohesive  attraction, 
and  to  project  the  parts  to  a  distance  with  great  violence. 

Besides  the  modes  already  described,  other  methods  are 
employed  to  retard  and  equalize  the  velocity  of  machinery. 
A  kind  of  fly  is  used  in  music  boxes,  and  in  the  striking  part 
of  clocks,  in  which  the  broad  surface  of  vanes,  upon  the  cir- 
cumference of  a  wheel,  is  made  to  act  against  the  air,  until  the 
resistance  becomes  equal  to  the  propelling  force,  so  that  the 
velocity  can  increase  no  further,  but  becomes  uniform.  Pen- 
dulums and  balances,  acted  on  through  the  different  kinds  of 
scapements,  are  also  means  of  equalizing  motion. 

FRICTION. 

A  part  of  the  force  by  which  machines  are  moved,  is  ex- 
pended in  overcoming  their  friction.  Hence  it  is  desirable  to 
obviate  as  far  as  possible  this  kind  of  resistance.  Friction  is 
supposed  to  arise  chiefly  from  the  roughness  and  inequality  of 
the  surfaces  of  bodies.  No  polish  can  be  given  to  a  surface 
mechanically,  so  fine  as  to  render  it  perfectly  smooth.  When 
surfaces  move  over  each  other,  a  certain  force  is  necessary  to 
disengage  the  minute  asperities  of  one  surface  from  those  of 
the  other,  either  by  causing  them  to  rise  over  each  other,  or  by 
bending  or  breaking  them  down. 

Friction  is  increased  by  the  roughness  of  bodies,  and  also 
by  the  force  with  which  they  are  pressed  together.  But  it  is 
very  little  affected  by  the  extent  of  the  surfaces  in  contact.  It 
is  greatest  at  the  moment  when  motion  begins ;  it  does  not, 
however,  change  afterwards  as  the  velocity  changes,  but  con- 
tinues to  retard  with  a  uniform  force,  whether  the  motion  per- 
formed be  slow  or  rapid.  There  are  several  points  in  regard 
to  friction  upon  which  writers  are  not  agreed. 

Friction  in  machinery  is  to  be  diminished  by  making  the 
surfaces  which  rub  upon  each  other  as  smooth  as  possible,  and 


262 


ELEMENTS  OF  MACHINERY. 


by  covering  them  with  some  unctuous  substance.  Black  lead 
in  fine  powder  is  sometimes  interposed  between  surfaces  to 
diminish  friction,  and  soapstone  applied  in  the  same  manner,  is 
still  more  useful.  It  is  supposed,  by  some,  that  different  me- 
tals moving  upon  each  other,  occasion  less  friction,  than  surfaces 
of  the  same  metal.  But  the  most  important  mode  of  diminish- 
ing friction,  is  to  employ  a  rolling,  or  turning  motion,  instead 
of  a  sliding  motion,  in  all  cases  where  it  is  practicable ;  and  by 
simplicity  of  construction  to  avoid  all  unnecessary  contact  of 
moving  surfaces. 

Remarks. — In  the  construction  of  machines  no  subject  is 
more  deserving  of  attention  than  simplicity  of  parts  and  struc- 
ture. The  more  complex  machines  are,  the  more  expensive 
they  are  to  erect,  the  more  liable  to  get  out  of  order,  and  the 
more  difficult  to  repair.  An  increased  expenditure  of  power 
is  also  occasioned  by  their  friction.  A  complex  machine  may 
evince  great  ingenuity  on  the  part  of  the  inventor,  and  may 
have  cost  much  labor  and  science  to  complete  it.  Yet  it  is  sure 
to  be  superseded,  the  moment  that  a  more  simple,  cheap,  or 
expeditious  way  of  attaining  the  same  object  is  discovered. 
The  improvement  of  the  mechanist  or  engineer  more  frequently 
consists  in  the  simplification  of  his  means,  than  it  does  in  the 
construction  of  complex  and  difficult  pieces  of  workmanship. 


Buchanan  on  Mill  Work  and  other  Machinery, 2  vols,  8vo.  1823  ;— 
Robison's  Mechanical  Philosophy,  vol.  ii.  p.  181; — Nicholson's 
Operative  Mechanic,  8vo.  1825 ;— Gregory's  Mechanics,  1826;— 
Brewster's  edition  of  Ferguson's  Mechanics,  1823; — Borgnis, 
Mechanique  Appliquee  aux  Arts,  4to.  Paris,  1818,  Tom.  3,  Composition 
des  Machines ; — Lanz  et  Bettancourt,  sur  la  Composition  des  Ma- 
chines, Fa^ris,  4to.  1819;— Hachette,  Traiie  Elementaire  des  Ma- 
chines ;— Leupold,  Theatrum  Machinarum  Universale,  7  vols,  folio, 
i^ipsic,  1724,  to  1774. 


CHAPTER  XII. 

OF  THE  MOVING  FORCES  USED  IN  THE  ARTS. 

Sources  of  Power. — It  is  the  office  of  machines  to  receive 
and  distribute  motion  derived  from  an  external  agent,  since  no 
machine  is  capable  of  generating  motion,  or  moving  power, 
v^ithin  itself.  The  sources  from  which  the  moving  power  ap- 
plied to  machinery  is  obtained,  are  various,  according  to  the 
nature  of  the  object,  and  the  amount  of  force  which  is  required. 
Men  and  animals,  water,  wind,  steam,  and  gunpowder  are  the 
principal  agents  employed  as  first  movers  in  the  arts.  Their 
power  may  be  ultimately  resolved  into  those  of  muscular  ener- 
gy, gravity,  heat,  and  chemical  affinity.  But  although  these 
are  the  sources  of  all  the  important  force  which  is  artificially 
employed  in  moving  large  masses  of  matter,  yet  certain  other 
agents  are  also  capable  of  producing  motion  upon  a  more  limit- 
ed scale,  such  as  magnetism,  electricity,  capillary  attraction,  he. 

Vehicles  of  Power. — Besides  the  original  forces  which  have 
been  mentioned,  there  are  certain  intermediate  agents  which 
serve  to  accumulate  and  transmit  power,  after  the  first  mover 
has  ceased  to  operate.  These  agents  commonly  act  either  by 
their  elasticity,  their  gravity,  or  their  inertia.  Springs  and 
compressed  air  are  examples  of  vehicles  acting  by  their  elasti- 
city, and  their  usefulness  continues  only  till  they  have  recover- 
ed the  situation  from  which  they  were  disturbed  by  another 
force.  In  like  manner  a  weight  acting  by  its  gravity  on  an 
axle  or  wheel,  prolongs  for  a  season  the  influence  of  the  power 
by  which  it  was  wound  up.  Fly  wheels  are  also  vehicles  which 
serve  by  their  inertia  to  continue  the  action  of  a  force  while  it  in- 
termits. Vehicles  of  power  are  highly  useful  in  equalizing  the 
irregularities  which  ai'e  incident  to  prime  movers,  in  prolonging 


254 


OF  THE  MOVING  FORCES  USED  IN  THE  ARTS. 


their  action  tlirough  convenient  periods  of  time,  and  in  multiply- 
ing the  modes  of  their  application. 

A  fundamental  distinction  among  mechanical  agents,  both 
original  and  secondary,  consists  in  this ;  that  in  some  the  inten- 
sity of  their  action,  or  the  acceleration  they  produce  in  a  given 
time,  is  the  same,  whether  the  body  acted  upon  be  at  rest  or 
in  motion  ;  in  others  it  is  greatest  when  the  body  acted  on  is  at 
rest,  and  becomes  less  as  its  velocity  increases.  Gravity  is  the 
only  force  which  is  certainly  known  to  act  with  equal  intensity 
on  bodies  in  motion,  and  at  rest ;  though  magnetism  probably 
possesses  the  same  property.  Every  other  important  power 
acts  more  forcibly  on  a  body  at  rest,  than  on  one  which  has 
already  acquired  motion  in  the  direction  in  which  it  acts.  * 
This  happens  with  the  strength  of  animals,  the  impulse  of  fluids, 
and  the  elasticity  of  springs. 

ANIMAL  POWER. 

Muscular  energy  is  exerted  through  the  contraction  of  the 
fibres  which  constitute  animal  muscles.  The  bones  act  as  levers 
to  facilitate  and  direct  the  application  of  this  force,  the  muscles 
operating  on  them  through  the  medium  of  tendons,  or  otherwise. 
Muscular  power  is  much  greater  in  some  animals,  than  it  is  in 
man,  owing  to  their  size,  or  more  active  mode  of  life.  It  is 
greatest  in  beasts  of  prey. 

Men, — The  power  of  a  man  to  produce  motion  in  weights 
or  obstacles,  varies  according  to  the  mode  in  which  he  applies 
his  force,  and  the  number  of  muscles  which  are  brought  into 
action.  In  the  operation  of  turning  a  crank,  a  man's  power 
changes  in  every  part  of  the  circle  which  the  handle  de- 
scribes. It  is  greatest  when  he  pulls  the  handle  upward  from 
the  height  of  his  knees,  next  greatest  when  he  pushes  it  down  on 
the  opposite  side,  though  here  the  power  cannot  exceed  the 
weight  of  his  body,  and  is  therefore  less  than  can  be  exerted  in 

*  See  Playfair's  Outlines  of  Natural  Philosophy,  vol.  i.  p.  107. 


OF  THE  MOVING  FORCES  USED  IN  THE  ARTS.  255 


pulling  upward.  The  weakest  points  are  at  the  top  and  bottom 
of  the  circle,  where  the  handle  is  pushed  or  drawn  horizontally. 

If  a  windlass  be  provided  with  two  cranks  placed  at  right 
angles  with  each  other,  two  men  will  perform  much  more  work, 
than  they  could  if  the  cranks  were  disconnected,  because  at  the 
moment  one  puts  forth  his  strength  to  the  least  advantage,  the 
other  is  exerting  his  with  the  greatest  effect. 

The  mode  in  which  a  man  can  exert  the  greatest  active 
strength,  is  in  pulling  upward  from  his  feet,  because  the  strong 
muscles  of  the  back  as  well  as  those  of  the  upper  and  lower 
extremities,  are  then  brought  advantageously  into  action,  and 
the  bones  are  favorably  situated  by  the  fulcra  of  the  levers  be- 
ing near  to  the  resistance.  Hence  the  action  of  rowing  is  one 
of  the  most  advantageous  modes  of  muscular  exertion,  and  no 
method  which  has  been  devised  for  propelling  boats  by  the  la- 
bor of  men,  has  hitherto  superseded  it. 

According  to  Mr  Buchanan,  the  comparative  effect  produced 
by  different  modes  of  applying  the  force  of  a  man,  is  nearly  as 
follows.  In  the  action  of  turning  a  crank,  his  force  may  be  re- 
presented by  the  number  17.  In  working  at  a  pump,  by  29. 
In  pulling  downward,  as  in  the  action  of  ringing  a  bell,  by  39. 
And  in  pulling  upward  from  the  feet,  as  in  rowing,  by  41.  * 

In  estimating  the  different  applications  of  animal  force,  we 
must  take  into  consideration  not  only  the  resistance  they  can 
overcome,  but  the  velocity  with  which  they  move,  and  the  length 
of  time  for  which  they  can  be  continued.  Violent  efforts  are 
not  true  specimens  of  a  man's  labor,  since  they  can  be  exerted 
for  a  short  time  only.  A  moderate  computation  of  an  ordinary 
man's  uniform  strength,  is  that  he  can  raise  a  weight  of  10  pounds 
to  the  height  of  10  feet  once  in  a  second,  and  continue  this  labor 
for  10  hours  in  the  day.  f  This  is  supposing  him  to  use  his 
force  under  common  mechanical  advantages,  and  without  any 
deduction  for  friction. 

*  See  Brewster's  Edition  of  Ferguson's  Mechanics,  vol.  ii.  p.  9.  The  whole 
numbers  are  1742,  2856,  3883,  and  4095. 

t  Young's  Lectures  on  Natural  Philosophy,  vol.  i.  p.  131. 


266  OF  THE  MOVING  FORCES  USED  IN  THE  ARTS. 

Horses. — Horses  are  often  employed  as  movers  of  machin- 
ery by  their  draught.  A  horse  draws  with  greatest  advantage 
when  the  line  of  draught  is  not  horizontal,  but  inclines  upward, 
making  a  small  angle  with  the  horizontal  plane,  as  already 
stated,  page  197.  The  force  of  a  horse  diminishes  as  his 
speed  increases.  The  following  proportions  are  given  by  Pro- 
fessor Leslie  for  the  force  of  the  horse  employed  under  differ- 
ent velocities.  If  his  force  when  moving  at  the  rate  of  two 
miles  per  hour,  is  represented  by  the  number  100,  his  force  at 
three  miles  per  hour  will  be  81, — at  four  miles  per  hour  64, — 
at  five  miles  49, — and  at  six  miles  36.  These  results  are  con- 
firmed very  nearly  by  the  observations  of  Mr  Wood.  ^  In  this 
way  the  force  of  a  horse  continues  to  diminish,  till  he  attains 
his  greatest  speed,  when  he  can  barely  carry  his  own  weight. 

Various  estimates  have  been  made  of  a  horse's  power,  by 
Desaguliers,  Smeaton,  and  others,  but  the  estimate  now  gener- 
ally adopted  as  a  standard  for  measuring  the  power  of  steam 
engines,  is  that  of  Mr  Watt,  whose  computation  is  about 
the  average  of  those  given  by  the  other  writers.  The  measure 
of  a  horse's  power,  according  to  Mr  Watt,  is,  that  he  can  raise 
a  weight  of  3S000  pounds  to  the  height  of  one  foot  in  a  minute. 

In  comparing  the  strength  of  horses  with  that  of  men,  Desa- 
guliers and  Smeaton  consider  the  force  of  one  horse  to  be  equal 
to  that  of  five  men  ;  but  writers  differ  on  this  subject. 

When  a  horse  draws  in  a  mill  or  engine  of  any  kind,  he  is 
commonly  made  to  move  in  a  circle,  drawing  after  him  the  end 
of  a  lever  which  projects  like  a  radius  from  a  vertical  shaft. 
Care  should  be  taken  that  the  horse-walk,  or  circle,  in  which 
he  moves,  be  large  enough  in  diameter,  for  since  the  horse  is 
continually  obliged  to  move  in  an  oblique  direction,  and  to  ad- 
vance sideways  as  well  as  forward,  his  labor  becomes  more 
fatiguing,  in  proportion  as  the  circle  in  which  he  moves  becomes 
smaller. 

In  some  ferry  boats  and  machines,  horses  are  placed  on  a 
revolving  platform,  which  passes  backward  under  the  feet 


*  Treatise  on  Rail  Roads,  p.  239. 


OF  THE  MOVING  FORCES  USED  IN  THE  ARTS.  257 

whenever  the  horse  exerts  his  strength  in  drawing  against  a 
fixed  resistance,  so  that  the  horse  propels  the  machinery  with- 
out moving  from  his  place.  A  horse  may  act  within  still  nar- 
rower limits,  if  he  is  made  to  stand  on  the  circumference  of  a 
large  vertical  wheel,  or  upon  a  bridge  supported  by  endless 
chains  which  pass  round  two  drums,  and  are  otherwise  support- 
ed by  friction  wheels.  Various  other  methods  have  been  prac- 
tised for  applying  the  force  of  animals,  but  most  of  them  are 
attended  with  great  loss  of  power,  either  from  friction,  or  from 
the  unfavorable  position  of  the  animal. 


WATER  POWER. 

Water  and  wind,  considered  as  prime  movers,  are  applica- 
tions of  the  force  of  gravity,  since  without  gravity  there  would 
be  neither  wind,  nor  currents  of  water.  The  force  of  water  is 
generally  applied  to  the  circumference  of  wheels,  which  it 
causes  to  revolve,  either  by  its  weight,  by  its  lateral  impulse,  or 
by  both  conjointly.  Water  wheels  are  generally  used  in 
one  of  three  forms.  These  are  the  overshot  wheel,  in  which 
the  water  descends  from  the  top  of  the  wheel  to  the  bot- 
tom ;  the  breast  wheel,  in  which  it  is  received  at  about  half  the 
height  of  the  wheel,  and  the  undershot  wheel,  where  it  acts  by 
the  impulse  of  a  current  flowing  under  the  wheel.  The  over- 
shot wheel  is  the  most  powerful  kind,  and  is  always  to  be  em- 
ployed where  a  sufficient  fall  of  water  can  be  obtained. 

Overshot  Wheel. — This  is  a  wheel,  or  drum,  the  circumfer- 
ence of  which  is  occupied  by  a  series  jp^^  ^ 
of  cavities,  commonly  called  buckets, 
into  which  the  water  is  delivered  from 
one  or  more  spouts  at  the  top  of  the 
wheel.  By  inspecting  Fig.  1,  it  will  be 
seen  that  the  buckets  on  one  side  of  the 
wheel  are  erect,  and  will  consequently 
become  loaded  with  water  ;  while  those 
on  the  other  side  are  inverted,  and  of 
33 


258  OF  THE  MOVING  FORCES  USED  IN  THE  ARTS. 


course  empty.  It  follows  that  the  loaded  side  will  always  pre- 
ponderate, and  by  descending  will  cause  the  wheel  to  revolve. 

If  it  were  possible,  says  Dr  Robison,  *  to  construct  the 
buckets  in  such  a  manner,  as  to  remain  completely  filled  with 
water  till  they  came  to  the  bottom  of  the  wheel,  the  pressure 
with  which  the  water  urges  the  wheel  round  its  axis,  would  be 
the  same  as  if  the  extremity  of  the  horizontal  radius  were  con- 
tinually loaded  with  a  quantity  of  water  sufficient  to  fill  a  square 
pipe,  whose  section  is  equal  to  that  of  the  bucket,  and  whose 
length  is  the  diameter  of  the  wheel.  But  such  a  state  of  things 
is  impossible,  and  if  a  bucket  be  fall  while  at  top,  it  will  begin 
to  lose  water  as  soon  as  it  turns  into  an  oblique  position,  and 
must  continue  to  do  so,  till  it  reaches  the  bottom. 

The  attention  of  engineers  has  been  directed  to  giving  the 
buckets  such  a  form  as  will  enable  them  to  retain  the  water 
for  the  longest  time  on  the  circumference  of  the  Fig.  2. 
wheel.  The  form  represented  in  Fig.  2,  answers  \\ 
this  purpose  tolerably  well,  and  from  its  simplicity  \\ 
is  the  one  most  commonly  used,  but  it  may  be  im-  i 
proved  still  farther  by  giving  an  additional  inclination  1 
inward  to  the  outer  edge  of  the  bucket,  as  seen  in  Fig.  3. 
Fig.  3.  As  the  best  economy  of  the  water  power 
requires  that  the  buckets  should  not  be  completely 
filled,  the  form  here  represented  will  retain  the  water 
until  it  has  descended  low  on  the  wheel.  To  pro- 
mote this  object  still  further,  Mr  Burns  has  divided 
the  bucket  by  a  partition  which  is  parallel  to  the  rim  of  the 
wheel,  constituting  one  bucket  within  another.  In  this  mode 
of  construction  the  water  does  not  enter  with  the  same  facilit)^ 
but  is  longer  in  escaping.  ^ 

In  order  to  prevent  the  inertia  of  the  water,  when  it  is  first 
laid  upon  the  buckets,  from  impeding  the  motion  of  the  wheel, 

*  Mechanical  Philosophy,  vol.  ii.  p.  592. 

t  We  are  informed  by  Dr  Brewster,  that  Burns's  improvement  has  not  been 
introduced  by  him  into  practice,  owing  to  the  difficulty  of  filling  the  inner 
buckets.    Mechanics,  vol.  ii.  p.  49. 


OF  THE  MOVING  FORCES  USED  IN  THE  AllTS.  259 

it  is  desirable  that  the  water  when  it  enters,  should  have  a  velo- 
city corresponding  as  nearly  as  possible  to  that  with  which  the 
wheel  is  revolving.  And  as  we  cannot  give  to  the  water  the 
direction  of  a  tangent  to  the  wheel,  the  velocity  with  which  it  is 
delivered  on  the  wheel,  must  be  so  much  greater  than  the  in- 
tended velocity  of  the  rim,  that  it  shall  be  equal  to  it  when  it 
is  estimated  in  the  direction  of  a  tangent.  To  facilitate  as 
much  as  possible  the  entrance  of  the  water,  it  is  common  to 
deliver  the  water  through  an  aperture,  which  is  divided  by  thin 
plates  of  board  or  metal,  placed  in  an  oblique  position  so  as  to 
direct  the  stream  of  water  into  the  buckets  in  the  most  perfect 
manner,  as  represented  in  Fig.  6.  In  order  to  detain  the 
water  as  long  as  possible,  the  lower  part  of  the  wheel  is  often 
made  to  revolve  in  a  concave  cavity  just  large  enough  to  receive 
it,  and  called  in  this  country,  the  apron,  as  seen  in  Fig.  9. 

A  difficulty  often  occurs  in  the  entrance  of  water  into  the 
buckets,  by  the  resistance  of  the  air  already  in  the  bucket, 
which  causes  the  water  to  regurgitate  and  spill.  This  evil  may 
be  entirely  prevented  by  making  the  spout  considerably  narrow- 
er than  the  wheel,  so  as  to  leave  room  for  the  escape  of  the  air 
at  the  two  ends  of  the  bucket. 

The  pressure  of  the  atmosphere  occasions  sometimes  a  seri- 
ous obstruction  to  the  motion  of  overshot  wheels,  by  causing  a 
quantity  of  back  water  to  be  lifted,  or  sucked  up,  by  the  as- 
cer.ding  inverted  bucket,  when  it  first  leaves  the  water.  This 
difficulty  is  remedied  by  making  a  few  small  holes  near  the 
base  of  the  bucket,  and  communicating  with  the  next  bucket. 
Through  these  the  air  will  enter  and  prevent  the  suction.  It 
is  true  that,  when  on  the  descending  side,  these  holes  will  allow 
the  escape  of  some  water,  but  as  this  water  only  flows  from 
one  bucket  to  the  next,  its  effect  is  inconsiderable  when  com- 
pared with  the  advantage  gained.  Air,  as  Professor  Robison 
observes,  will  escape  through  a  hole  about  30  times  faster  than 
water,  under  the  same  pressure. 

With  respect  to  variations  in  the  fall,  the  same  writer  remarks 
that  since  the  active  pressure  is  measured  by  the  pillar  of  water 


260 


OF  THE  MOVING  FORCES  USED  IN  THE  ARTS. 


reaching  from  the  horizontal  plane  where  it  is  delivered  on  the 
wheel,  to  the  horizontal  plane  where  it  is  spilled  by  the  wheel, 
it  is  evident  that  it  must  be  proportionate  to  this  pillar,  and 
therefore  we  must  deliver  it  as  high  and  retain  it  as  long  as 
possible.  This  maxim  obliges  us  to  use  a  wheel  whose  diam- 
eter is  equal  to  the  whole  fall.  We  shall  not  gain  anything  by 
employing  a  larger  wheel,  for  although  we  should  gain  by  using 
only  that  part  of  the  circumference,  where  the  weight  will  act 
more  perpendicularly  to  the  radius,  we  shall  lose  more  by  the 
necessity  of  discharging  the  water  at  a  greater  height  from  the 
bottom.  * 

Chain  Wheel, — ^When  there  is  a  very  small  supply  of  water 
falling  from  a  very  great  head,  the  double  overshot  wheel,  with 
a  chain  of  buckets,  is  a  valuable  machine.  This  wheel  is  re- 
presented in  Fig.  4,  where  two  rag  wheels  Fig.  4. 
are  placed,  one  at  top,  and  the  other  at 
bottom,  and  a  series  of  buckets  are  fixed  to 
an  endless  chain,  the  Hnks  of  which  fall  into 
notches  in  the  circumference  of  the  rag 
wheels.  The  water  issuing  from  the  mill 
course  is  introduced  into  the  buckets  on  one 
side  at  top.  The  descent  of  the  loaded 
buckets  on  this  side  puts  the  rag  wheels  in 
motion,  and  the  power  is  conveyed  from 
the  shaft  of  the  upper  wheel,  to  turn  any 
kind  of  machinery.  When  the  buckets 
reach  the  bottom  they  allow  the  water  to  escape,  and  ascend- 
ing empty  on  the  opposite  side,  they  again  return  to  the  spout 
to  be  filled  as  before.  In  this  machine,  the  buckets  have  in 
every  part  of  their  path  the  same  mechanical  effect  to  turn  the 


*  Mechanical  Philosophy,  vol.  ii.  p.  600. 

On  this  subject  Dr  Brewster  remarks,  that  if  we  employ  a  wheel  the 
diameter  of  which  is  higher  than  the  fall,  we  may  take  advantage  of  any  cas- 
ual rise  of  the  water  above  its  usual  level,  and  by  a  particular  form  of  the  de- 
livering sluice,  introduce  the  water  higher  upon  the  wheel  and  thus  actually 
increase  the  height  of  the  fall. 


OF  THE  MOVING  FORCES  USED  IN  THE  ARTS.  261 

wheels,  and  they  do  not  allow  the  water  to  escape  till  they  have 
reached  almost  the  lowest  part  of  the  fall. 

This  species  of  wheel  possesses  another  advantage,  namely, 
that  by  raising  the  lower  wheel  and  taking  out  two  or  three  of 
the  buckets  it  may  be  made  to  work  when  there  is  such  a  quan- 
tity of  back  water  as  would  otherwise  prevent  it  from  moving. 

Dr  Robison,  has  described  a  machine  of  this  kind,  in  which 
plugs,  or  horizontal  floatboards,  are  fixed  to  a  chain.  On  the 
descending  side  these  plugs  pass  through  a  tube,  alitde  greater 
in  diameter  than  that  of  the  floats,  and  the  water  acting  upon 
these  floats  as  it  does  in  the  case  of  a  breast  wheel,  gives  mo- 
tion to  the  two  rag  wheels. 

In  regard  to  the  most  advantageous  velocity  to  be  produced 
with  a  given  quantity  of  water  in  an  overshot  wheel,  various 
mathematicians  have  concluded,  that  the  slower  a  wheel  moves, 
the  greater  is  its  power  of  performance.  But  the  experiments 
of  Mr  Smeaton  lead  to  the  conclusion,  that  in  practice  there  is 
a  hmit  of  velocity,  and  that  overshot  wheels  do  most  work 
when  their  circumferences  move  at  the  rate  of  about  three  feet 
in  a  second. 

Undershot    Wheel, — An   undershot  Fig.  5. 

water  wheel,  is  a  wheel  furnished  with 
a  series  of  plane  surfaces,  called  floats 
or  floatboards,  projecting  from  its  circum- 
ference for  the  purpose  of  receiving  the 
impulse  of  the  water,  which  is  deliver- 
ed by  a  proper  canal,  with  great  velocity, 
upon  the  under  part  of  the  wheel.  A 
wheel  of  this  kind  is  represented  in  Fig.  5. 

When  an  undershot  wheel  is  put  in  motion  by  a  stream  of 
water  striking  against  one  of  its  floatboards,  in  a  direction  at 
right  angles  with  the  radius,  the  action  of  the  water  will  dimin- 
ish, as  the  velocity  of  the  wheel  increases,  till  at  last  the  mo- 
mentum of  the  water,  or  of  the  accelerating  force,  is  just  equal 
to  the  momentum  of  the  resistance,  or  of  the  retarding  force. 
The  motion  of  the  wheel  will  then  become  uniform. 


262  OF  THE  MOVING  FORCES  USED  IN  THE  ARTS. 

By  calculation  it  appears  that  a  machine  thus  driven  by  the 
impulse  of  a  stream  produces  the  greatest  effect,  or  does  most 
work  in  a  given  time,  when  the  wheel  moves  with  one  third  of 
the  velocity  with  which  the  water  moves.  *  But  in  practice 
this  rule  is  liable  to  some  variation,  for  the  water  does  not  es- 
cape as  soon  as  it  has  given  its  impulse,  but  is  confined  by  the 
channel  for  some  time,  and  acts  with  a  variety  of  influences. 
In  Mr  Smeaton's  experiments,  which  are  cited  as  authorities 
by  most  writers  since  his  time,  it  was  found  that  an  undershot 
wheel  when  working  to  the  greatest  advantage,  had  a  velocity 
which  varied  from  one  third  to  one  half  the  velocity  of  the 
stream  }  and  that  in  great  machines  it  was  nearer  to  the  latter 
of  these  hmits,  than  the  former. 

It  is  advantageous  that  the  size  of  undershot  wheels  should  be 
as  great  as  circumstances  will  permit,  and  it  ought  never,  says 
Dr  Brewster,  to  be  less  than  seven  times  the  natural  depth  of 
the  stream  at  the  bottom  of  the  course,  f  In  regard  to  the 
best  number  of  floatboards  a  difference  of  opinion  has  prevail- 
ed, but  it  is  now  generally  admitted  that  the  more  floatboards 
a  wheel  has,  the  greater  and  more  uniform  will  be  its  effect.  J 
According  to  the  experiments  of  Bossut,  it  appeared  that  a 
'wheel  with  48  floatboards  produced  a  greater  effect  than  one 
with  24,  and  the  latter  a  greater  effect  than  one  with  12. 
Smeaton's  experiments  justify  the  same  conclusion,  though  he 
found  that  on  adapting  to  the  wheel  a  circular  sweep  of  such 
length,  that  one  floatboard  entered  into  the  curve,  before  an- 
other left  it,  the  effect  came  so  near  to  the  former,  as  not  to 
give  any  hopes  of  advancing  it  by  increasing  the  number  of 
floats  beyond  24  in  the  wheel  experimented  on.  § 

In  regard  to  the  position  of  the  floatboards,  they  should  not 
be  in  the  direction  of  the  radius,  but  inclined  from  it  slightly 
backwards.   From  the  experiments  of  Deparcieux  and  Bossut, 

*  Playfair's  Outlines  of  Natural  Philosophy,  vol.  i.  p.  214 — and  Robison, 
622. 

t  Ferguson's  Mechanics,  vol.  ii.  p.  17. 

t  Gregory's  Mechanics,  vol.  i.  p.  462.  §  Ibid.  p.  476. 


I 


OF  THE  MOVING  FORCES  USED  IN  THE  ARTS.  203 

it  appears  that  there  is  a  very  sensible  advantage  gained  by  in- 
clining the  floatboards  to  the  radius  of  the  wheel  about  20  de- 
grees, so  that  the  lowest  floatboard  shall  not  be  perpendicular, 
but  have  its  point  turned  up  the  stream  about  20  degrees. 
This  inclination  causes  the  water  to  heap  up  along  the  float- 
board,  and  act  by  its  weight.  *  The  floats  should  for  this 
purpose  be  made  much  broader  in  the  direction  of  the  radius 
than  the  vein  of  water  which  they  intersect,  is  deep.  Another 
advantage  attending  this  obliquity  of  the  floats  is,  that  they  are 
less  resisted,  when  they  rise  out  of  the  water. 

The  best  way  of  delivering  the  water  on  an  undershot  wheel 
in  a  close  mill  course,  according  to  Dr  Robison,  is  to  let  it  slide 
down  a  very  smooth  channel  without  touching  the  wheel,  till  it 
arrives  near  the  bottom,  at  which  place  the  wheel  should  be 
exactly  fitted  to  the  course.  The  floats  should  be  broader 
than  the  depth  of  the  water,  so  as  never  to  be  wholly  immersed, 
but  allowing  the  intercepted  water  to  heap  up  against  them. 
If  the  bottom  of  the  course  be  an  arc  of  a  circle  having  a  great- 
er radius  than  that  of  the  wheel,  the  water  which  slides  down 
will  be  gradually  intercepted  by  the  floats,  or  strike  upon  more 
than  one  at  a  time.  In  this  country  it  is  often  the  practice  to 
admit  the  water  directly  from  the  bottom  of  a  pond,  or  reser- 
voir, instead  of  causing  it  to  glide  down  a  separate  channel 
from  near  the  top  ;  and  this  method  is  found  very  effectual. 

Back  Water. — The  back  water,  or  tail  water,  is  that  portion 
which  has  past  by  the  wheel.  This  portion  is  not  only  useless, 
but  in  most  cases  injurious,  since  by  its  inertia  and  weight,  it 
resists  the  escape  of  the  floats  and  empty  buckets  in  their  pas- 
sage upward.  Its  effect  is  increased  in  times  of  floods  or  fresh- 
ets, so  that  it  is  often  necessary  to  place  wheels  higher  than 
they  otherwise  would  be,  to  provide  against  it.  A  method  of 
getting  rid  of  back  water  in  times  of  flood,  has  been  invented 
by  Mr  Perkins  in  this  country,  and  Mr  Burns  in  Scotland.  It 
consists  in  a  separate  passage  by  which  a  current  of  water  is 


*  Robison's  Mechanical  Philosophy,  vol.  ii.  p.  625. 


264  OF  THE  MOVING  FORCES  USED  IN  THE  ARTS. 


taken  from  the  mill-lead,  or  flume,  as  at  A  in  Fig.  6,  and  pass- 
Fig.  6. 


es  with  great  rapidity  under  the  wheel,  and  thence  under  the 
flooring  at  B.  This  rapid  current  has  the  effect  to  take  off 
and  carry  away  the  back  water  from  beneath  the  wlieel,  while 
it  is  prevented  from  returning  by  the  force  of  the  same  current, 
and  the  barrier  at  C.  The  water  which  is  expended  to  main- 
tain this  current  is  no  more  than  would  run  over  the  waste  gate 
in  a  time  of  freshet. 

Besanfs  Wheel. — To  diminish  the  retardation  occasioned 
by  back  water,  Mr  Besant  has  invented  a  wheel  in  which  the 
floats  are  placed  obliquely  in  a  double  row,  pi^^  ^ 
as  in  Fig.  7,  where  the  wheel  is  represent- 
ed as  seen  edgeways.  Each  pair  of  floats 
forms  an  acute  angle  open  at  its  vertex. 
By  this  construction  the  floats  escape  more 
gradually  and  with  less  resistance  from  the 
back  water,  and  likewise  the  resistance  of 
the  atmosphere  is  prevented,  by  the  admis- 
sion of  air  at  the  open  angle  of  the  floats. 

Lamherfs  Wheel. — As  water  acts  most  advantageously  upon 
undershot  wheels,  when  the  floats  are  perpendicular  to  the  sur- 
faces of  the  stream,  it  has  been  attempted  in  different  ways  to 
keep  them  always  in  a  vertical  position.  In  the  method  pro- 
posed by  Mr  Lambert,  the  floats  are  hung  upon  hinges  or  piv- 
ots at  the  extremities  of  the  spokes,  and  are  kept  in  a  vertical 
position  by  a  large  iron  ring  which  is  suspended  from  the  lower 


OF  THE  MOVING  FORCES  USED  IN  THE  ARTS.  2G5 

extremities  of  the  whole,  and  is  allowed  to  pass  during  the 
revolution  through  a  slit  in  the  middle  of  each  float.    In  Fig. 
8,  is  a  view  of  one  side  of  the  wheel 
with  the  ring  attached.    A  is  the  ^^S-  ^^ 

centre  of  the  wheel,  B  B  are  spokes 
or  arms  of  the  water  wheel,  C  D, 
C  D  are  the  floatboards  which  are 
here  seen  edgeways.  E  E  is  a 
large  iron  ring  connected  by  joints 
to  the  lower  extremity  of  all  the 
floatboards,  and  serving  by  its 
weight  to  keep  them  in  a  vertical 
position.  This  wheel  is  probably 
too  complicated  for  common  use. 
The  iron  ring  is  kept  from  moving 
sideways  by  guides,  or  friction 
wheels,  placed  at  each  side. 

Breast  Wheel. — The  breast  wheel  is  intermediate  between 
the  overshot  and  undershot  wheels,  having  the  water  delivered 
upon  it  at  about  half  its  height,  or  at  the  ^.  ^ 

level  of  its  axis.  In  breast  wheels  in 
England,  buckets  are  not  commonly 
employed,  but  the  floatboards  are 
fitted  accurately,  with  as  little  play  as 
possible,  to  the  mill  course,  so  that 
the  water,  after  acting  upon  the  float- 
boards  by  its  impulse,  is  detained  be- 
tween them  in  the  mill  course,  and 
acts  by  its  weight  till  it  reaches  the  lowest  part  of  tlie  wheel. 
A  breast  wheel  is  represented  in  Fig.  9,  as  it  is  often  construct- 
ed in  this  country  with  buckets,  instead  of  floats,  and  with  a 
part  of  its  circumference  fitted  to  the  mill  course,  or  apron. 

Horizontal  Wheel. — A  horizontal  wheel  with  oblique  floats, 
sometimes  called  in  this  country  a  tub  wheel,  is  turned  by  a 
current  of  water  discharged  against  the  floats  in  the  manner  re- 


34 


26G  OF  THE  MOVINQ  FORCES  USED  IN  THE  ARTS. 


presented   in   Fig.    10.  Fig.  10. 

This  method  is  said  to  be 
in  common  use  on  the 
continent  of  Europe,  and 
but  seldom  employed  in 
England.  It  is  a  disad- 
vantageous mode  of  ap- 
plying power,  and  is  only 
recommended  in  corn- 
mills  by  its  simplicity,  the 
millstones  being  turned  directly  by  the  axis  of  the  water  wheel, 
without  the  intervention  of  other  wheels,  or  gearing.  In  the 
same  manner  another  kind  of  tub  wheel,  which  is  a  sort  of  in- 
verted cone  furnished  with  spiral  floats  on  its  inside,  is  made  to 
revolve  horizontally,  by  discharging  into  it  a  current  of  water 
from  above. 

Barker's  Mill — This  machine,  which  is  also  sometimes 
called  Parent's  mill,  is  driven  by  an  application  of  the  force  of 
water  different  from  any  of  those  which  have  been  already  de- 


Fig. 


11. 


77Z 


scribed.  This  application  con- 
sists, not  in  the  direct  use  of  the 
weight,  or  impulse,  of  water,  but 
in  that  of  its  reaction,  or  counter  ^ 
pressure.  The  principle  of  this 
simple  machine  may  be  seen  by 
inspecting  Fig.  11,  where  CD  is 
a  revolving  vertical  tube,  carrying 
a  millstone  m  on  the  upper  part 
of  its  axis.  At  the  bottom  of  this 
tube  is  a  horizontal  tube  A  B,  at 
the  extremities  of  which  are  two 
apertures  A  and  B,  opening  in 
opposite  directions.  A  stream  of  water  is  introduced  from  the 
mill  course  above,  and  flows  out  at  the  apertures  at  A  and  B, 
and  in  this  way  keeps  up  a  continued  horizontal  rotary  motion 
around  the  axis  D  m. 


OF  THE  MOVING  FORCES  USED  IN  THE  ARTS.  267 

In  order  to  understand  how  this  rotary  motion  is  produced, 
we  may  suppose  the  apertures  to  be  shut,  and  the  tube  C  D 
filled  with  water.  The  area  of  the  apertures  A  and  B  will  then 
be  pressed  outward  by  a  force  equal  to  a  column  of  water 
whose  height  is  C  D,  and  whose  base  is  equal  to  the  area  of 
the  apertures.  Every  part  of  the  tube  A  B  sustains  a  similar 
pressure ;  but  as  these  pressures  are  balanced  by  equal  and 
opposite  pressures,  the  machine  remains  at  rest.  But  when 
the  aperture  at  B  is  opened,  the  pressure  at  that  place  is  re- 
moved, and  therefore  the  area  will  be  carried  round  in  a  direc- 
tion opposite  to  that  of  the  aperture,  by  a  pressure  which  is 
due  to  the  height  of  the  column  and  area  of  the  aperture. 
The  same  thing  happens  with  the  other  area,  and  the  two  pres- 
sures carry  round  the  vertical  axis  in  the  same  direction. 

An  improvement  has  been  made  in  Barker's  mill  by  dis- 
pensing with  the  tube  C  D,  retaining  only  its  axis  ;  and  intro- 
ducing the  water  on  the  under  side  of  the  transverse  tube  at  D. 
For  this  purpose  the  water  is  brought  down  from  the  reservoir 
at  E,  by  a  separate  passage,  and  introduced  at  D  through  a  water 
joint,  which  suffers  the  arms  of  the  tube  to  revolve  without  much 
loss  of  water.  Such  a  passage  is  represented  by  the  shaded 
part  E  F  D.  The  upward  pressure  of  the  water  may  be  made 
to  support  a  great  part  of  the  weight  of  the  machine. 

WIND  POWER. 

Currents  of  water,  being  limited  in  magnitude,  can  be  con- 
fined in  their  action  to  one  side  of  a  wheel.  But  it  is  not  easy 
to  do  the  same  with  currents  of  wind,  on  account  of  their  in- 
definite magnitude,  and  the  difficulty  of  screening  one  half  of 
the  wheel  advantageously  from  their  action.  It  is  therefore 
common  to  employ  vertical  windmills,  having  a  number  of  sails 
placed  obliquely  to  the  wind,  and  turning  on  a  horizontal  axis 
which  is  parallel  to  the  wind,  or  nearly  so.  The  action  of  the 
wind  in  this  case  is  resolved  into  two  forces,  and  since  the  sails 
cannot  obey  the  first  by  moving  in  the  direction  of  the  wind, 
they  obey  the  second  and  move  at  right  angles  with  it. 


268 


OF  THE  MOVING  FORCES  USED  IN  THE  ARTS. 


Vertical  Windmill. — The  common  windmill  has  usually 
four  sails,  and  sometimes  six  or  eight.  The  power  of  these 
sails  to  turn  their  axis  depends,  when  other  things  are  equal, 
upon  their  degree  of  obliquity  in  regard  to  the  wind.  The  an- 
gle which  is  most  effectual  for  giving  motion  to  the  sails  from  a 
state  of  rest,  is  an  angle  of  35-1-  degrees  with  the  weather,  or  with 
the  plane  in  which  the  sails  revolve.  *  But  the  angle  which  pro- 
duces the  greatest  action  upon  a  sail  at  rest,  is  not  the  most  ef- 
fectual when  a  sail  is  in  motion.  As  the  motion  increases,  the 
action  of  the  wind  diminishes,  and  in  order  to  preserve  this  ac- 
tion, the  sails  require  to  be  brought  nearer  to  the  wind.  And 
since  each  part  of  the  sail,  in  revolving,  has  a  different  velocity, 
those  parts  which  are  nearest  the  circumference,  being  swiftest, 
are  not  acted  upon  so  powerfully  by  the  wind,  as  those  which 
are  nearer  the  centre  ;  on  which  account  it  is  useful  to  give 
the  sails  a  slight  spiral  curvature,  so  as  to  make  the  angle  with 
the  weather  at  the  extremity  of  the  sail,  less  than  it  is  at  the 
centre.  When,  however,  the  sails  are  perfectly  plane,  it  is  ad- 
vantageous, according  to  Mr  Smeaton,  that  the  angle  of  the 
sails  with  the  weather,  should  be  18  degrees,  or  less  ;  in  other 
words,  that  their  angle  with  the  axis  should  be  72  degrees,  or 
more.  The  velocity  of  the  sails  in  this  case  at  their  outer  ex- 
tremity, is  often  found  to  be  more  than  twice  that  of  the  wind. 

Adjustment  of  Sails. — On  account  of  the  inconstant  nature 
of  the  motion  of  the  wind,  it  is  necessary  to  have  some  provi- 
sion for  accommodating  the  resistance  of  the  sails,  to  the  degree 
of  violence  with  which  the  wind  blows.  This  is  commonly 
done  by  clothing  and  unclothing  the  sails ;  that  is,  by  covering 
with  canvass  or  thin  boards,  a  greater  or  smaller  portion  of  the 
frame  of  the  sails,  according  to  the  force  of  the  wind  at  differ- 
ent times.  A  method  has  been  devised  for  producing  the  same 
effect,  by  altering  the  obliquity  of  the  sails  ;  and  windmills 
have  been  so  made,  as  to  regulate  their  own  adjustment,  by  the 
force  of  the  wind.    If  we  suppose  a  windmill,  or  wind  wheel,  to 

^  Determined  by  Parent — see  Brewster's  Ferguson's  Meclianics,  vol.  ii.  p.  69 


OF  THE  MOVING  FORCES  USED  IN  THE  ARTS.  2G9 

consist  of  four  arms,  and  that  the  sails  were  connected  to  these 
arms  at  one  edge,  by  means  of  springs ;  the  yielding  of  these 
springs  would  allow  the  sails  to  turn  back,  when  the  wind  should 
blow  with  violence  ;  and  their  elasticity  would  bring  them  up  to 
the  wind  whenever  its  force  abated.  This  effect  has  been  pro- 
duced by  a  weight  acting  on  the  sails  through  a  series  of  levers. 
A  loose  iron  rod,  passing  through  the  centre  of  the  axle  of  the 
windwheel,  receives  the  action  of  the  weight  at  one  end,  and 
communicates  it  to  the  sails  at  the  other. 

Sometimes  a  governor  like  that  described  on  page  249,  is 
used  to  regulate  the  velocity  of  windmills  which  are  built  for 
grinding,  by  increasing  the  supply  of  corn  to  be  ground,  or  of 
work  to  be  done,  whenever  the  force  of  the  wind  increases. 
The  governor  is  also  applied  in  a  very  ingenious  manner  to 
furl  or  unfurl  a  portion  of  the  sails,  thus  accommodating  them 
to  variations  of  the  wind. 

As  it  is  necessary  that  a  windmill  should  face  the  wind  from 
whatever  point  it  blows,  the  whole  machine,  or  a  part  of  it, 
must  be  capable  of  turning  horizontally.  Sometimes  the  whole 
mill  is  made  to  turn  upon  a  strong  vertical  post,  and  is  there- 
fore called  a. post  mill;  but  more  commonly  the  roof,  or  head 
only,  revolves,  carrying  with  it  the  windwheel  and  its  shaft,  the 
weight  being  supported  on  friction  rollers.  In  order  that  the 
wind  itself  may  regulate  the  position  of  the  mill,  a  large  vane, 
or  weathercock,  is  placed  on  the  side  which  is  opposite  the 
sails,  thus  turning  them  always  to  the  wind.  But  in  large  mills 
the  motion  is  regulated  by  a  small  supplementary  windwheel, 
or  pair  of  sails,  occupying  the  place  of  the  vane,  and  situated 
at  right  angles  with  the  principal  windwheel.  When  the  wind- 
mill is  in  its  proper  position,  with  its  shaft  parallel  to  the  wind, 
the  supplementary  sails  do  not  turn.  But  when  the  wind 
■  changes,  they  are  immediately  brought  into  action,  and  by 
turning  a  series  of  wheelwork,  they  gradually  bring  round  the 
head  to  its  proper  position. 

As  the  resistance  occasioned  by  the  side  of  the  building 
makes  a  difference  in  the  force  of  the  wind  upon  the  upper 


370  OF  THE  MOVING  FORCES  USED  IN  THE  ARTS. 

and  under  sails,  it  is  common  to  incline  the  sails,  and  their  ax- 
is, in  such  a  manner  that  the  lower  sails  shall  be  farther  from 
the  building,  than  they  would  be  if  in  a  vertical  position. 

Horizontal  Windmill. — This  name  is  given  to  those  wind- 
mills which  turn  on  a  vertical  axis.  Various  methods  are  em- 
ployed in  their  construction,  in  most  of  which  the  wind  acts  by 
its  direct  impulse,  as  in  an  undershot  water  wheel.  In  the 
most  common  forms,  the  sails,  like  floatboards,  present  their 
broadside  to  the  wind  on  the  acting  side  of  the  wheel,  but  are 
folded  up,  or  turned  edgewise  on  the  returning  side.  These 
wheels,  however,  are  found  to  be  greatly  inferior  to  the  vertical 
windmill,  in  the  amount  of  work  which  they  are  capable  of 
performing,  and  at  the  present  day  they  are  little  used. 

As  wind  is  the  most  uncertain  of  all  the  moving  agents,  and 
fails  totally  in  times  of  calm,  it  is  not  common  to  depend  upon 
this  power  in  large  works,  provided  other  moving  forces  can 
be  obtained.  The  steam  engine  has  in  many  cases  superseded 
it,  but  it  is  still  used  in  certain  places  for  grinding  corn,  pump- 
ing water,  and  driving  inferior  machinery.  Upon  the  ocean  it 
is  a  locomotive  agent  of  incalculable  importance. 

* 

STEAM  POWER. 

Steam. — The  power  of  steam  depends  on  the  tendency  which 
water  possesses  to  expand  into  vapor,  when  heated  to  a  cer- 
tain temperature.  Many  other  substances,  and  perhaps  all, 
have  the  same  tendency,  and  those  which  are  volatile  at  low 
temperatures  might  doubtless  be  made  the  sources  of  moving 
power  in  the  arts.  But  since  water,  which  is  the  most  cheap 
and  abundant  of  these  substances,  fortunately  possesses  also 
the  greatest  number  of  requisites  for  an  expansive  agent,  it  is 
not  likely  to  be  superseded  by  any  other  material. 

When  water  is  converted  into  steam,  it  expands  to  about 
1700  times  its  original  volume,  *  so  that  a  cubic  inch  of  water 

*  1633  times,  according  to  Gay-Lussac.  See  Ure's  Dictionary,  article  Calo- 
ric.— 1711  times  according  to  Tredgold. 


OF  THE  MOVING  FORCES  USED  IN  THE  ARTS.  271 

furnishes  about  a  cubic  foot  of  steam,  at  212  degrees  of  Fahr- 
enheit, under  the  common  pressure  of  the  atmosphere.  Water 
cannot,  however,  be  converted  immediately  into  steam  by  the 
application  of  a  boiling  temperature,  but  requires  a  certain  pe- 
riod to  effect  its  volatilization.  This  period  is  about  six  times 
as  great,  as  that  which  is  necessary  to  raise  it  from  the  freezing 
to  the  boiling  point,  supposing  the  supply  of  heat  to  be  uniform. 
The  amount  of  heat  which  is  absorbed,  or  rendered  latent,  by 
the  conversion  of  water  into  steam,  is  about  950  degrees.  ^ 

The  power  of  steam  to  produce  motion  in  other  bodies,  de- 
pends upon  the  increase  of  its  own  volume,  and  whatever  body 
resists  this  increase  will  be  acted  upon  by  a  force  proportionate 
to  the  elastic  power  of  the  steam,  and  the  circumstances  un- 
der which  the  resistance  is  made.  In  a  vessel  boiling  in  the 
open  air  we  are  not  sensible  of  the  magnitude  of  this  force,  be- 
cause the  steam,  and  the  resisting  medium  against  which  it 
acts,  are  both  invisible.  But  when  we  consider  that  the  steam 
when  first  generated,  has  to  lift  off  from  the  water,  before  it  can 
assume  its  elastic  form,  the  weight  of  the  superincumbent 
atmosphere,  and  that  this  weight  in  the  atmospheric  column 
which  presses  on  a  vessel  only  two  feet  in  diameter,  is  equal  to 
several  tons,  w^e  may  easily  conceive  of  the  force  which  attends 
this  expansion. 

Furthermore,  since  steam  has  the  property  of  immediately 
condensing  into  water,  as  soon  as  its  temperature  is  reduced 
below  212  degrees,  it  follows  that  the  atmospheric  weight 
which  has  been  lifted  by  the  formation  of  the  steam,  will 
immediately  fall,  when  the  steam  condenses ;  and  with  a  force 
equal  to  that  by  which  it  was  raised.  This  furnishes  an  indi- 
rect or  secondary  application  of  the  power  of  steam. 

But  the  powers  of  steam  are  not  limited  by  the  effects  which 
it  produces  at  the  common  boiling  temperature.  If  steam  be 
separated  from  the  contact  of  water,  and  exposed  to  a  farther 
increase  of  temperature,  it  will  continue  to  expand  by  the  law 


*950  according  to  Watt,— 967,  Ure. 


272 


OF  THE  MOVING  FORCES  USED  IN  THE  ARTS. 


which  governs  the  increase  of  all  gaseous  bodies,  and  will 
double  its  volume  once  for  every  480  degrees  of  Fahrenheit's 
thermometer.  *  And  furthermore,  if  water  itself  be  inclosed 
in  strong  vessels  and  thus  heated,  its  expansive  force  will  be 
prodigiously  greater  than  that  of  steam  alone,  since  every  par- 
ticle of  the  water  tends  to  generate  steam  of  high  temperature, 
and  to  occupy  the  space  which  is  due  to  such  steam.  In  a 
common  boiler  containing  water  and  steam,  each  addition  of 
caloric  causes  a  fresh  portion  of  steam  to  rise,  and  to  add  its 
elastic  force  to  that  of  the  steam  previously  existing,  so  that  an 
excessive  pressure  is  soon  exerted  against  the  inside  of  the 
vessel,  if  the  augmentation  of  heat  has  been  considerable.  At 
212  degrees  Fahrenheit,  steam  has  an  elastic  force  equal  to  the 
pressure  of  the  atmosphere.  If  it  be  farther  heated  in  contact 
with  water,  it  will  have  a  force  equal  to  that  of  two  atmospheres 
at  about  250  degrees,  of  four  atmospheres  at  293  degrees,  and 
of  eight  atmospheres  at  344  degrees.  These  are  the  results  in 
round  numbers  of  Mr  Southern's  experiments,  and  they  are 
nearly  confirmed  by  those  of  Drs  Robison  and  Ure. 

At  temperatures  below  212  degrees,  steam  has  still  a  certain 
elastic  force  which  discovers  itself  whenever  the  pressure  of 
the  atmosphere  is  taken  off.  Thus  its  elastic  force  at  180  de- 
grees is  equal  to  about  half  an  atmosphere,  and  it  has  some 
force  at  all  temperatures  above  the  freezing  point. 

Steam  expands  in  all  directions  alike,  and  is  useful  as  a  mov- 
ing agent,  only  by  its  pressure.  It  cannot,  like  water  and  wind, 
be  made  to  act  advantageously  by  its  impulse  in  the  open  air, 
for  the  momentum  of  so  light  a  fluid,  unless  generated  in  vast 
quantities,  would  be  inconsiderable.  Some  of  ihe  earliest  at- 
tempts, however,  at  forming  a  steam  engine,  consisted  in  direct- 
ing the  current  of  steam  from  the  mouth  of  an  eolipile,  against 
the  vanes  or  floats  of  a  revolving  wheel,  f  In  order  that  the 
pressure  of  steam  may  be  rendered  available  in  machinery,  the 
steam  must  be  confined  within  a  cavity  which  is  air-tight,  and 

*  Ure's  Dictionary  of  Chemistry,  Art.  Caloric  and  Gas. 

t  Such  was  the  ene;inc  of  Branca  in  the  beginning  of  the  17th  century. 


OF  THE  MOVING  FORCES  USED  IN  THE  ARTS.  273 


SO  constructed  that  its  dimensions,  or  capacity,  may  be  altered 
without  altering  its  tightness.  ,  When  the  steam  enters  such  a 
vessel,  it  enlarges  the  actual  cavity,  by  causing  some  moveable 
pari  to  recede  before  it,  and  from  this  moveable  part,  motion  is 
communicated  to  machinery.  A  hollow  cylinder  having  a 
moveable  piston  accurately  fitted  to  its  bore,  constitutes  a  ves- 
sel of  this  kind.  It  was  used  more  than  a  century  ago  by 
Newcomen,  and  as  it  is  found  to  combine  more  advantages 
than  any  other  kind  of  arrangement  for  motion,  its  use  has 
never  been  superseded.  The  piston  thus  employed  has  a  re- 
ciprocating motion,  which  is  converted,  when  necessary,  into  a 
rotary  one,  by  the  appropriate  mechanism. 

Applications  of  Steam. — The  pressure  of  steam  is  capable 
of  being  applied  to  use  in  three  different  ways,  and  these  modes 
have  giv^en  rise  to  some  of  the  most  important  varieties  of  the 
steam  engine.  The  three  mediods  which  are  used  for  obtaining 
power  from  steam  are,  1.  By  condensation,  as  in  the  atmos- 
pheric engine.  2.  By  generation,  as  in  the  simple  high  pres- 
sure engines.  3.  By  expansion,  as  in 
WoolPs  engine,  Watt's  expansion  engine, 
and  some  others.  These  methods  have 
been  illustrated  by  Mr  Tredgold  by  a 
figure  like  that  in  the  margin.  Suppose 
a  cylindric  vessel  A  B  C  D  to  be  placed 
in  a  vertical  position,  with  a  given  depth 
of  water  in  the  bottom,  and  an  air-tight 
piston  above  the  water  balanced  b}^  a 
weight  D  equal  to  its  ow^n  weight  and 
friction.  In  this  state  let  heat  be  applied 
to  the  base  A  C  ;  then  as  the  water  be- 
comes converted  into  steam  of  slightly 
greater  force  than  the  atmospheric  pres- 
sure, the  piston  will  rise  till  the  whole 
water  is  in  a  state  of  steam.  It  must  be 
observed,  however,  that  the  generation 
of  this  steam,  which  is  of  atmospheric 
35 


274  OF  THE  MOVING  FORCES  USED  IN  THE  ARTS. 

elastic  force,  affords  no  available  power,  but  is  simply  sufficient 
to  balance  the  column  of  atmospheric  air,  and  exclude  it  from 
a  given  height  of  the  cylinder. 

By  Condensation. — In  the  state  of  things  just  described,  if 
the  steam  be  suddenly  condensed  into  water  by  the  application 
of  cold,  it  is  obvious  that  the  piston  will  be  driven  downward 
with  a  force  equal  to  the  weight  of  the  atmosphere  which  pres- 
ses on  the  piston,  and  through  a  distance  equal  to  that  which 
the  piston  had  been  raised  by  the  generation  of  steam.  It  fol- 
lows that  the  power  of  steam  which  is  of  atmospheric  elastic 
force,  is,  when  speedily  condensed,  directly  proportionate 
to  the  space  which  it  occupies.  If  the  temperature  of  this 
steam  be  raised  above  212  degrees^  it  will  occupy  a  larger 
space,  the  increase  being  equal  to  the  expansion  of  steam  by 
the  given  change  of  temperature.  But  a  quantity  of  heat 
nearly  equivalent  to  the  increase  of  volume  will  be  absorbed, 
and  hence,  says  Mr  Tredgold,  the  effect  of  a  given  quantity  of 
fuel  would  not  be  increased  by  the  expedient.  * 

By  Generation. — Suppose  the  same  cylinder  and  apparatus 
to  have  heat  applied  to  its  base,  with  only  the  difference  of  the 
piston  being  loaded  with  a  given  pressure  per  inch  of  its  area. 
The  generation  of  the  steam  v/ill  raise  the  loaded  piston,  but 
the  height  through  which  it  will  be  raised  will  be  less  than  if  it 
were  not  loaded.  The  steam  having  to  act  in  opposition  both 
to  the  pressure  of  the  atmosphere  and  the  load  on  the  piston, 
the  space  it  will  occupy  will  be  in  the  inverse  ratio  of  the  pres- 
sures which  oppose  it,  supposing  the  steam  of  atmospheric 
elastic  force  to  have  been  of  the  same  temperature.  Thus,  if 
the  load  on  the  piston  be  equal  to  twice  the  atmospheric  pres- 
sure, the  piston  will  be  raised  only  one  third  of  the  height,  but 
on  rapid  condensation  it  descends  with  three  times  the  pressure, 
and,  therefore,  whether  the  steam  be  generated  of  atmospheric 
elastic  force,  or  of  a  greater  force,  the  power  it  affords  by  gen- 
eration and  condensation  is  the  same  at  the  same  temperature, 
and  this  power  is  directly  as  the  elastic  force  of  the  steam,  mul- 


*  Tredgold  on  the  Steam  Engine,  p.  157 — 159. 


OF  THE  MOVING  FORCES  USED  IN  THE  ARTS.  275 


tiplied  by  the  space  it  occupies,  supposing  that  the  motion  of 
the  piston  is  rectilinear. 

But  if,  as  in  the  last  case,  a  loaded  piston  be  raised,  and  then 
a  valve  be  opened  which  allows  the  steam  to  escape,  the  whole 
power  gained  will  be  equal  only  to  the  weight  raised,  descend- 
ing from  the  height  to  which  it  was  raised ;  and  the  power 
which  would  have  resulted  from  condensation  will  be  lost,  and 
the  loss  is  equal  to  the  pressure  of  the  atmosphere  acting  through 
the  height  to  which  the  piston  was  raised  by  the  steam.  This 
is  the  nature  of  the  common  high  pressure  steam  engine.  It  is 
obvious,  that  the  greater  the  elastic  force  of  the  steam,  the  less 
is  the  proportionate  loss  by  neglecting  to  condense  it  under 
these  circumstances  ;  but,  it  may  be  remarked,  that  unless  the 
valve  aperture  be  equal  to  the  diameter  of  the  cylinder,  the 
steam  cannot  escape  at  the  necessary  rate  without  part  of  the 
load  acting  to  expel  it ;  and  so  much  more  of  the  effective 
force  will  of  course  be  lost.  The  effective  power  is  as  the 
space  the  steam  occupies,  multiplied  by  the  excess  of  elastic 
force  above  the  atmospheric  pressure. 

By  Expansion. — Retaining  the  same  loaded  piston,  let  it  be 
raised  by  the  conversion  of  a  given  quantity  of  water  into  steam, 
to  the  height  which  corresponds  to  the  load  and  temperature. 
Then  if  the  load  on  the  piston  be  wholly  removed  at  that  height, 
the  steam  will  raise  the  piston  by  expanding  till  it  becomes 
nearly  of  the  same  elastic  force  as  the  atmosphere,  and  its  con- 
densation will  produce  the  same  effect  as  if  the  steam  had  been 
generated  of  atmospheric  elastic  force  at  first.  Consequently, 
the  effect  in  raising  the  load  on  the  piston  is  wholly  additional, 
and  the  joint  effect  of  a  high  pressure  and  condensing  engine  is 
produced  by  the  same  steam.  Hence  by  this  combination  of 
effect,  the  power  of  steam  of  high  elastic  force  will  be  nearly 
doubled. 

This  is  not,  however,  the  mode  by  which  steam  can  be  ap- 
plied with  the  greatest  advantage  ;  for  instead  of  removing  the 
load  on  the  piston  wholly  at  the  height  to  which  it  w^as  raised 
by  the  generation  of  the  high  pressure  steam,  a  part  of  it  may 


276  OF  THE  MOVING  FORCES  USED  IN  THE  ARTS. 

be  removed,  and  then  the  steam  would  expand  to  a  height  de- 
pending on  the  portion  of  the  load  removed  ;  at  that  height  re- 
move a  second  portion,  and  so  on,  successively,  till  the  steam 
becomes  of  atmospheric  elastic  force.  In  this  case,  as  far  as 
the  load  was  raised  in  parts  by  the  expansion  of  the  steam,  the 
effect  is  greater  than  in  the  preceding  combination.  This  il- 
lustrates the  principle  of  the  high  pressure  expansion  engines  of 
Evans,  Woolf,  and  some  others. 

Again,  let  the  piston  be  raised  unloaded,  as  in  the  first  case, 
by  the  conversion  of  a  certain  quantity  of  water  into  steam  of 
atmospheric  elastic  force.  When  the  piston  is  at  that  height, 
add  a  weight  equal  to  half  the  atmospheric  pressure  to 
the  line  passing  over  the  pulley.  Then  the  elastic  force  of  the 
steam  being  unbalanced,  the  piston  would  rise  till  that  elastic 
force  would  be  half  the  atmospheric  pressure,  or  till  the  piston 
would  be  at  double  its  former  height.  Now  suppose  the  steam 
to  be  condensed,  and  the  weight  removed  from  the  pulley  at  the 
same  instant.  Then  the  power  of  the  descent,  after  deducting 
the  power  added  to  produce  the  ascent,  will  be  one  half  more 
than  it  would  have  been  by  simply  condensing  steam  of  atmos- 
pheric elastic  force.  This  illustrates  the  principle  of  the  ex- 
pansion engines  of  Hornblower  and  Watt ;  and  it  differs  from 
the  principle  of  Woolf  in  using  steam  only  of  low  pressure. 
The  weight  added  to  the  line  passing  over  the  pulley  is  intro- 
duced here  merely  to  exemplify  the  mode  of  applying  a  portion 
of  the  excess  of  power  which  is  accumulated  in  the  fly  wheel, 
in  one  part  of  the  operation,  to  assist  the  machine  through  the 
rest. 

It  has  been  assumed  that  steam  at  least  of  atmospheric  elas- 
tic force  was  generated,  but  this  is  not  a  necessary  condition, 
for  it  frequently  occurs  that  engines  work  with  steam  of  less 
elastic  force.  The  same  mode  of  illustration  will  show  whence 
this  happens.  Let  half  the  pressure  of  the  atmosphere  on  the 
piston  be  balanced  by  a  weight  over  a  pulley.  Then  on  the 
application  of  heat,  steam  of  half  the  atmospheric  elastic  force 
would  be  generated,  and  raise  the  piston  to  double  the  height 


OF  THE  MOVING  FORCES  USED  IN  THE  ARTS.  277 

that  it  would  be  raised,  in  common  cases,  by  steam  capable  of 
supporting  the  atmospheric  pressure.  Consequently  on  its  being 
condensed,  the  descending  force  will  be  half  the  atmospheric 
pressure  acting  through  double  the  height;  and  the  steam 
produces  the  same  effect  as  before. 

The  foregoing  methods  of  the  application  of  steam  will  be 
found  apparent  in  the  different  forms  of  the  steam  engine,  in 
which  they  have  been  called  into  use. 

The  Steam  Engine. — The  steam  engine  is  a  machine  by 
which  the  power  derived  from  steam  is  converted  to  practical 
use.  It  has  occupied  the  attention  of  philosophers  and  artists 
for  more  than  a  century^  and  is  now  brought  to  so  great  a  de- 
gree of  perfection  as,  in  the  opinion  of  many  scientific  men,  to 
leave  little  probability  of  its  further  improvement.  Whether 
viewed  with  reference  to  the  great  skill  which  has  been  em- 
ployed in  perfecting  it,  or  the  importance  and  extent  of  its  ap- 
plication, it  may  justly  be  view^ed  as  the  noblest  production  of 
the  arts  in  modern  times.  For  acquiring  a  clear  conception  of 
the  steam  engine  as  it  is  now  commonly  constructed,  it  will  be 
useful  to  consider,  first,  the  boiler  in  which  the  power  is  gener- 
ated, and  secondly  the  engine  in  which  it  is  directed  and 
applied  to  use. 

Boiler. — On  account  of  the  gradual  rate  at  which  water 
boils  away,  it  is  necessary  in  most  engines  to  keep  a  large  quan- 
tity constantly  heated,  to  afford  steam  with  sufficient  rapidity 
for  its  consumption  by  the  engine.  This  water  is  inclosed  in  a 
strong  tight  vessel,  called  the  boiler,  which  is  made  of  iron  or 
copper,  and  rests  in  contact  with  a  furnace.  It  is  requisite, 
that  a  boiler  should  be  of  sufficient  strength  to  resist  the  great- 
est pressure  which  is  ever  liable  to  occur  from  the  expansion  of 
the  steam.  It  must  also  offer  a  sufficient  extent  of  surface  to 
the  fire,  to  insure  the  requisite  amount  of  vaporization.  In 
common  low  pressure  boilers,  it  requires  about  eight  feet  of 
surface  of  the  boiler  to  be  exposed  to  the  action  of  the  fire  and 
flame,  to  boil  off  a  cubic  foot  of  water  in  an  hour,  and  a  cubic 


278 


OF  THE  MOVING  FORCES  USED  IN  THE  ARTS. 


foot  of  water  thus  converted  into  steam  is  equal  to  a  one-horse 
power.  * 

The  strongest  form  for  a  boiler,  and  one  of  the  earhest  which 
was  used,  is  that  of  a  sphere,  but  this  form  is  the  one  wliich  of- 
fers least  surface  to  the  fire.  The  figure  of  a  cyUnder  is  on 
many  accounts  the  best,  and  it  is  now  extensively  used,  espe- 
cially for  engines  of  high  pressure.  It  has  the  advantage  of 
being  easily  constructed  from  sheets  of  metal,  and  the  form  is 
of  equal  strength  except  at  the  ends.  In  such  a  boiler,  the 
ends  should  be  made  thicker  than  the  other  parts.  The  fur- 
nace is  so  constructed  that  the  flame  and  hot  smoke  may  pass 
under  the  whole  length  of  the  boiler,  and  afterwards  around 
both  its  sides,  before  escaping  to  the  chimney. 

In  what  are  called  flue  boilers,  a  cylindrical  furnace  is  placed 
within  a  cylindrical  boiler,  so  that  the  fuel  is  surrounded  by 
water  on  all  sides,  and  communicates  to  it  nearly  all  its  heat, 
except  the  portion  wdiich  passes  up  the  chimney. 

In  large  engines,  which  are  of  low  pressure,  the  form  of  the 
boiler,  which  was  used  by  Mr  ,  Watt,  still  continues  to  be  em- 
ployed, particularly  in  England.  In  this  boiler  the  upper  half 
is  a  semicylinder,  while  the  lower  half  is  nearly  rectangular, 
with  the  under  side  concave,  so  that  a  cross  section  would 
nearly  resemble  a  horse-shoe.  This  boiler  is  less  strong  than 
those  of  a  cylindrical  form,  but  it  offers  a  larger  surface  to  the 
fire,  without  occupying  much  more  space.  A  boiler  of  this 
kind,  as  it  is  fitted  up  in  large  engines,  with  appendages  for  reg- 
ulating its  own  fire,  water,  and  steam,  is  represented  in  PL  VIII. 
Fig.  5.  A  part  of  the  furnace  is  supposed  to  be  taken  away, 
to  bring  the  boiler  into  view,  and  also  a  portion  of  the  boiler  is 
removed  to  show  its  inside. 

Appendages. — In  the  figure  above  referred  to,  B  B  B  B  is 
the  boiler,  made  of  thick  sheets  or  plates  of  rolled  iron  strongly 
rivetted  together,  a  part  of  which  are  removed  to  show  the 
interior.    It  is  supposed  to  be  half  full  of  water  at  the  boiling 

*  See  Tredgold  on  the  Steam  Engine,  with  the  following  correction,  p.  124, 
line  2  from  the  bottom.    For  steam  read  water. 


OF  THE  MOVINO  FORCES  USED  IN  THE  ARTS. 


279 


temperature.  C  is  the  steam  gcmge  the  object  of  which  is  to 
determine  the  degree  of  pressure  acting  within  the  boiler.  It 
is  a  bent  iron  tube,  or  inverted  syphon,  one  end  of  which  com- 
municates with  the  boiler,  and  the  other  end  with  the  atmos- 
phere. The  tube  is  partly  filled  with  mercury,  and  as  the 
pressure  of  the  steam  increases,  the  mercury  will  be  driven 
outward  and  will  rise  in  the  external  leg  of  the  syphon.  As 
the  height  of  the  column  of  mercury  cannot  be  seen,  the  tube 
being  opaque,  a  small  wooden  stem  is  made  to  float  in  the  tube, 
with  its  end  projecting  by  the  side  of  a  graduated  scale.  Every 
inch  in  height  which  the  stem  rises,  shows  a  difference  of  two 
inches  in  the  two  surfaces  of  the  mercury  in  the  tube,  and  in- 
dicates a  pressure  of  about  a  pound  upon  every  square  inch  of 
the  inner  surface  of  the  boiler.  And  as  low  pressure  engines 
are  seldom  worked  with  more  than  three  or  four  ])ounds  to  the 
square  inch,  the  mercury  seldom  rises  higher  than  three  or  four 
inches  in  such  engines.  In  high  pressure  engines,  the  mercu- 
rial guage  is  not  so  easily  applied,  for  these  engines  are  fre- 
quently worked  at  a  pressure  of  several  atmospheres,  and  each 
additional  atmosphere  requires  an  addition  of  nearly  15  inches 
to  the  column  of  mercury. 

W  is  a  large  opening  called  the  man  hole,  of  sufficient  size 
to  permit  a  man  to  enter  the  boiler  to  clean  or  examine  it.  It 
is  closed  by  a  strong  iron  plate.  D  is  the  steam  pipe  which 
conveys  the  steam  to  the  engine.  It  is  provided  with  a  throttle 
valve,  which  is  a  circular  disc,  or  partition,  turning  on  an  axis, 
and  connected  with  the  governor  described  on  page  249.  Its 
use  is  to  regulate  the  supply  of  steam  by  closing  the  pipe,  if  the 
engine  goes  too  fast,  or  by  opening  it,  if  it  is  too  slow\  F  F 
are  the  guage  cocks  which  indicate  the  height  of  water  in  the 
boiler.  Their  extremities  stand  at  different  depths  in  the  boil- 
er, one  being  below  the  surface  of  the  w^ater,  and  the  other 
above  it.  When  the  water  is  at  the  proper  height,  one  of  these 
will  emit  steam,  on  being  opened,  and  the  other  will  emit  water. 
They  are  frequently  placed  on  the  end  instead  of  the  top  of 
the  boiler. 


280  OF  THE  MOVING  FORCES  USED  IN  THE  ARTS. 

For  keeping  up  a  regular  supply  of  -water  to  the  boiler,  a 
vertical  tube  G  called  the  feed  pipe  is  used.  Upon  its  top  is  a 
small  cistern  H  H  H  H,  which  is  kept  full  of  water  by  a  pump 
worked  by  the  engine.  At  the  bottom  of  this  cistern  is  a  valve 
E,  connected  to  one  end  of  the  lever  a  h.  At  the  other  end 
of  this  lever  is  a  wire  a  c,  which  passes  through  a  steam-tight 
opening  at  c?,  and  supports  a  stone  float  c  upon  the  surface  of 
the  water,  the  stone  being  counterbalanced  by  a  weight  at  the 
valve  e.  When  the  w^ater  lowers  in  the  boiler,  the  stone  float 
descends  and  by  acting  upon  the  lever  a  b,  opens  the  valve  e. 
Water  immediately  flows  in  from  the  cistern  and  continues  to 
do  so,  till  the  float  rises  and  shuts  the  valve.  It  wiW  be  observ- 
ed that  the  column  of  water  in  the  feed  pipe  must  be  suffi- 
ciently high  to  counterbalance  the  pressure  of  steam  in  the 
boiler.  On  this  account  it  cannot  be  applied  in  high  pressure 
engines,  without  making  it  of  a  very  inconvenient  height.  In 
these  engines,  therefore,  water  is  supplied  to  the  boiler  by  ? 
small  forcing  pump,  worked  by  one  of  the  reciprocating  parts 
of  the  engine ;  and  it  is  frequently  heated  before  being  pumped 
in,  that  it  may  not  check  the  production  of  steam. 

For  the  purpose  of  regulating  the  fire,  the  feed  pipe  is  fur- 
nished with  an  iron  bucket  O,  hung  by  a  chain  which  passes 
over  two  pullies  P  P,  and  is  attached  by  its  other  extremity  to 
an  iron  damper  A,  which  commands  the  chimney.  When  the 
steam  in  the  boiler  is  urged  to  too  great  an  extent,  it  forces  the 
water  upward  in  the  feed  pipe  and  causes  the  iron  bucket  to 
ascend.  This  lowers  the  damper  into  the  smoke  flue,  and  by 
thus  intercepting  the  current  of  air,  checks  the  force  of  the  fire. 
In  some  boilers  the  passage,  which  brings  air  to  the  fire,  is  in- 
tercepted, instead  of  the  smoke  flue. 

To  prevent  the  boiler  from  bursting,  if  by  accident  the  pres- 
sure of  the  steam  should  become  too  great  for  the  strength  of 
the  boiler,  a  safety  valve  is  provided  at  S,  opening  outward.  It 
is  kept  down  by  a  weight,  so  that  it  cannot  be  raised  except  by 
a  greater  force  than  that  which  is  required  to  work  the  engine. 
It  is  highly  important,  however,  that  it  should  not  be  liable  to 


OF  THE  MOVING  FORCES  USED  IN  THE  ARTS.  281 

any  other  weight  or  incumbrance,  than  that  which  the  engine 
requires,  and  to  prevent  this  danger  it  is  inclosed  in  a  case 
which  is  kept  locked.  When  the  engine  stops  working,  or  the 
steam  is  generated  too  rapidly  for  its  expenditure,  the  safety 
valve  rises,  and  the  superfluous  steam  rushes  out  with  a  hissing 
noise. 

Another  safety  valve  is  also  provided,  which  differs  from  the 
preceding  in  opening  inwards.  It  is  kept  up  by  a  counter 
weight  on  a  lever,  and  its  use  is  to  prevent  the  weight  of  the 
atmosphere  from  crushing  in  the  sides  of  the  boiler,  when  the 
engine  stops  working,  and  the  steam  cools. 

As  boilers  are  usually  proved  before  being  submitted  to 
use,  the  accident  of  bursting  does  not  happen  from  a  general 
want  of  strength,  unless  the  safety  valve  be  overloaded.  It  is 
most  likely  to  happen  either  from  neglect,  in  suffering  the  water 
to  get  too  low,  so  that  the  metal  is  softened  by  heat,  or  else 
from  the  corrosion  of  the  metal  in  places,  by  oxidation,  after 
long  exposure  to  the  fire.  If  a  sediment  is  suffered  to  accu- 
mulate to  a  considerable  depth  on  the  bottom  of  the  boiler,  it 
has  the  effect  to  exclude  the  water  from  contact  with  the  metal, 
so  that  the  metal  becomes  hotter,  and  is  more  rapidly  oxidated, 
and  even  softened,  by  the  heat. 

Besides  the  forms  of  the  boiler  already  mentioned,  various 
others  have  been  employed,  such  as  combinations  of  tubes,  and 
other  figures,  intended  to  multiply  surface,  for  the  purpose  of 
raising  more  steam  from  the  same  amount  of  water,  in  a  given 
time.  They  have  been  applied  in  some  high  pressure  engines, 
but  in  most  cases,  the  simpler  forms  are  preferred.  In  Per- 
kins's engine,  a  strong  vessel  called  a  generator,  is  kept  full  of 
water  heated  to  a  high  temperature.  Portions  of  the  water 
are  successively  forced  out,  and  reliance  is  placed  on  the  heat 
already  in  this  water,  to  produce  from  it  the  requisite  amount 
of  steam. 

Engine. — The  steam  being  generated  in  sufficient  quantities 
in  the  boiler,  it  is  next  applied  to  use  in  the  working  or  moving 
part,  which  we  have  called  the  engine.    Of  this  engine  a  great 
36 


282 


OF  THE  MOVTNfJ  FORCES  USED  IN  THE  ARTS. 


variety  of  forms  and  modifications  have  been  proposed  and 
adopted,  at  different  times.  A  few  of  those  which  are  effectual 
in  their  principle,  and  most  extensively  employed,  will  now  be 
considered. 

JYoncondensing  Engine. — The  simplest  form  of  the  steam 
engine,  is  that  of  the  noncondensing,  commonly  called  the  high 
pressure  engine.  In  this  engine,  the  apparatus  for  condensa- 
tion is  dispensed  with,  and  the  steam  is  worked  at  a  high  tem- 
perature, and  afterwards  discharged  into  the  open  air.  Of 
course  a  part  of  the  force  of  the  steam  is  expended  in  over- 
coming the  pressure  of  the  atmosphere,  and  the  surplus  only 
can  be  applied  to  drive  machinery.  That  this  surplus  may  be 
sufficient  to  produce  the  requisite  power,  a  pressure  of  30  or 
40  pounds  on  a  circular  inch,  above  the  atmospheric  pressure, 
is  commonly  kept  up  in  these  engines.  * 

The  manner  in  which  the  engine  is  made  to  operate,  is 
briefly  as  follows.  The  steam  in  escaping  from  the  boiler  to 
the  open  air,  is  obliged  to  pass  through  the  cylinder,  the  cavity 
of  which  is  closed,  except  where  it  communicates  with  the 
valves.  By  the  opening  and  shutting  of  these  valves,  the 
steam  is  made  to  enter  the  cylinder  alternately  at  each  end,  and 
escape  by  the  opposite  end.  But  in  doing  this,  its  passage  is 
always  intercepted  by  the  piston,  so  that  before  it  can  escape, 
it  must  move  the  piston  from  one  end  to  the  other  of  the  cy- 
linder. The  repetition  of  this  movement  gives  motion  to  a 
beam,  or  other  alternating  part,  from  which  it  is  communicated 
by  a  connecting  rod  and  crank,  to  a  fly  wheel,  in  the  same 
manner  as  is  seen  in  the  condensing  engine,  PI.  IX.  hereafter 
to  be  described.  The  figure  there  represented  may  be  con- 
sidered as  a  noncondensing  engine,  if  we  remove  from  it  the 
condenser  and  its  appendages,  occupying  the  lower  part  of  the 
plate.  B  represents  the  boiler,  C  the  pipe  which  conveys  the 
steam,  D  the  cylinder,  E  the  piston,  F  the  beam,  h  the  crank, 
G  the  fly  wheel. 

*  See  Trcdgold  on  the  Steam  Engine,  p.  181. 


OF  THE  MOVING  FORCES  USED  IN  THE  ARTS. 


283 


The  different  apparatus  of  valves,  by  which  the  entrance 
and  escape  of  steam  is  regulated,  also  the  other  ap])endages  of 
the  engine,  will  be  considered  in  another  place.  In  arranging 
the  time  of  their  opening  and  shutting,  it  is  usual  to  allow  not 
quite  all  the  steam  to  escape  at  the  end  of  the  stroke.  A  small 
portion  is  retained  to  receive  the  shbck  of  the  piston,  and  by- 
its  elasticity  to  destroy  its  momentum,  and  cause  it  to  recoil 
back  without  loss  of  force. 

Noncondensing  engines  sometimes  work  by  the  generative 
force  of  steam,  and  sometimes  by  the  generative  and  expansive 
force.  They  are  used  in  cases  where  simplicity  and  lightness 
is  required,  as  in  locomotive  engines ;  also  in  situations  where 
a  sufficient  supply  of  water  for  condensation  cannot  easily  be 
obtained.  They  are  inferior  in  safety  to  condensing  engines, 
yet  as  they  cost  much  less  at  the  outset  for  the  expense  of 
building,  they  are  often  preferred  for  small,  or  temporary 
works.  In  proportion  to  the  high  temperature  at  which  the 
steam  is  worked,  great  caution  is  necessary  in  regard  to  the 
strength  and  management  of  the  boiler  in  these  engines. 

Condensing  Engines, — Engines  of  this  class  are  fitted  up 
with  an  apparatus  for  condensing  the  steam  into  water,  so  that 
a  vacuum,  -nearly  complete,  is  formed  in  one  part  of  the  cylin- 
der, just  before  the  stroke  of  the  piston  into  that  part  takes 
place.  By  this  construction  the  resistance  of  the  atmosphere 
is  avoided,  and  thus  the  power  of  the  engine  to  perform  work, 
is  much  increased.  The  steam  also  is  sufficiently  powerful 
for  use,  at  compatively  low  temperatures,  and  hence  arises  the 
increase  of  safety  which  is  found  in  low  pressure  engines,  a  name 
given  to  those  condensing  engines,  which  are  w^orked  with 
steam  of  moderate  elastic  force. 

In  the  atmospheric  engine,  invented  by  Newcomen,  the  pis- 
ton was  raised  by  the  steam,  aided  by  a  counter  weight,  till  it 
arrived  at  the  top  of  the  cylinder,  which  was  left  perfectly 
open.  A  jet  of  water  was  then  admitted  into  the  bottom  of 
the  cylinder,  which  suddenly  condensed  the  steam,  so  that,  a 
vacuum  being  formed,  the  piston  was  driven  down  by  a  force 


284 


OF  THE  MOVING  FORCES  USED  IN  THE  ARTS. 


equal  to  the  weight  of  the  column  of  superincumbent  air.  The 
water  was  now  excluded  by  a  stop  cock,  and  the  steam  read- 
mitted. The  piston  was  thus  again  raised,  and  the  process  re- 
peated as  before. 

A  great  inconvenience  attended  this  method,  arising  from 
the  circumstance,  that  the  cylinder  itself  required  to  be  heated 
and  cooled  at  each  stroke  of  the  piston,  thus  occasioning  great 
delay,  and  an  unnecessary  expense  both  of  fuel  and  of  cold 
water.  To  remedy  this  evil,  Mr  Watt  invented  the  separate 
condenser,  which  is  a  strong  vessel  situated  at  a  distance  from 
the  cylinder,  but  communicating  with  it  by  a  pipe,  so  as  to 
form  with  it  a  common  cavity,  without  reducing  materially,  its 
temperature.  Into  this  vessel  the  jet  of  cold  water  is  thrown, 
and  as  all  the  communicating  pipes  are  governed  by  valves,  or 
cocks,  the  cylinder  below  the  piston  is  alternately  filled  with 
steam  from  the  boiler,  and  emptied  of  steam  by  the  condenser. 

In  the  double  acting  engine,  invented  by  Mr  Watt,  the  top  of 
the  cylinder  was  closed,  and  rendered  air-tight,  the  rod  of  the 
piston  only  passing  through  it.  Thus  the  cylinder  is  divided 
by  the  piston  into  two  cavities,  both  communicating  with  the 
boiler,  and  both  with  the  condenser.  By  the  aid  of  valves,  an 
alternate  communication  is  kept  up,  so  that  the  steam  being  al- 
ternately admitted  at  both  ends,  impels  the  piston  successively 
in  both  directions,  while  the  condenser,  at  the  same,  time  de- 
stroys the  resistance.  In  this  engine,  compared  with  the  single 
engine  of  Mr  Watt,  which  was  previously  in  use,  a  double 
quantity  of  steam  is  used,  and  a  double  power  exerted  in  the 
same  space  and  time. 

Description, — In  PI.  IX,  is  a  view  of  a  double  acting  steam 
engine,  nearly  as  constructed  by  Murray,  and  upon  the  same 
general  principles  as  those  of  Mr  Watt,  varying,  however,  in 
the  valves,  and  some  other  particulars. 

A  represents  the  furnace,  which  is  here  shown  in  section,  as 
is  also  the  boiler  above  it,  and  all  the  principal  cavities  of  the 
engine.  The  flame  and  hot  smoke,  after  passing  underneath 
the  boiler  for  its  whole  length,  return  through  the  side  passages 
d  d,  before  they  are  discharged  into  the  chimney. 


OF  THE  MOVING  FORCES  USED  IN  THE  ARTS.  285 

B  is  the  boiler,  which,  in  this  example,  is  of  a  cylindrical 
form,  a  shape  better  adapted  for  strength  than  that  represented 
in  PI.  VIII.  The  appendages  represented  in  PI.  VIII.  are  not 
here  repeated.  Some  of  them,  indeed,  are  not  used  in  steam 
boats,  and  in  small  engines.  The  boiler  is  commonly  made  of 
sheets  of  iron,  strongly  rivetted  together  and  tightened  by  ham- 
mering. If  intended  to  contain  salt  water,  the  boiler  is  made 
of  copper,  to  prevent  corrosion. 

C  C  C  is  the  steam  pipe,  which  carries  the  steam  from  the 
boiler  to  the  cylinder  through  the  valve  I.  It  is  made  of  cast 
iron,  and  its  joints  screwed  together  by  flanges. 

D  is  the  cylinder,  communicating  by  passages  at  the  top  and 
bottom  with  the  valve  I.  The  cylinder  is  made  of  cast  iron, 
and  accurately  bored  to  make  its  inner  surface  smooth  and  true. 

E  the  piston,  which,  by  its  rod  e,  gives  an  alternating  motion 
to  the  beam//,  about  its  centre  F,  the  other  end  of  which,  by 
another  connecting  rod  g,  gives  motion  to  the  heavy  fly-wheel 
G  G,  by  means  of  a  crank  h.  Thus,  after  the  engine  has  be- 
gun to  work,  its  power  is  accumulated  in  the  fly  wheel,  and  a 
circular  motion  may  be  communicated  from  it  to  any  machinery. 

H  is  an  eccentric  circle  on  the  axle  of  the  fly  wheel  G. 
It  gives  motion  through  the  medium  of  its  levers  w  x  and 
y and  the  connecting  rods  xy  and  zl,  in  a  manner 

easily  understood,  by  inspection,  to  the  valve  I. 

I  is  a  coffer  valve,  capable  of  sliding  up  and  down,  and  hav- 
ing a  cavity  on  the  side  next  the  cylinder.  By  moving  up  and 
down  it  opens  and  shuts  the  passages,  and  admits  the  steam 
alternately  to  each  end  of  the  cylinder  ;  and  at  the  same  time 
forms  a  communication  between  the  opposite  end  and  the  con- 
denser. 

W  is  the  governor,  which  regulates  the  speed  of  the  engine. 
It  resembles  the  governor  described  in  Chap.  XI,  but  has  its 
moveable  collar  on  the  top  at  s.  It  may  be  turned  by  a  band 
from  the  axle  of  the  fly  wheel,  or  placed  directly  over  the  axle, 
and  geared  to  it  by  bevel  wheels.  When  the  fly  wheel  moves 
too  fast,  the  balls  of  the  governor  recede  from  their  centre,  and 


286 


OF  THE  MOVING  FORCES  USED  IN  THE  ARTS. 


by  acting  on  tlie  lever  r  s,  cause  it  to  turn  upon  its  fulcrum  t, 
and  partially  to  close  the  steam  pipe  by  a  throttle  valve  at  K. 
When  the  velocity  abates,  th&  balls  subside,  and  the  valve 
opens  so  as  to  admit  more  steam. 

L  is  the  air  pump,  the  use  of  which  is  to  discharge  the  air 
and  water  which  collect  in  the  condenser,  M. 

M  is  the  condenser,  which  is  an  empty  cylindrical  vessel 
immersed  in  a  cistern  of  cold  water,  S  S,  and  communicating 
with  the  cylinder  by  the  pipe  O.  It  has  a  valve  or  cock  com- 
municating with  the  cistern,  and  moved  by  the  rod  gg,  through 
which  a  jet  of  cold  water  enters  it  for  the  purpose  of  condensing 
the  steam. 

N  a  small  cistern,  filled  with  water.  Into  this  cistern  enters 
a  pipe  from  the  condenser  M,  the  top  of  which  pipe,  is  covered 
by  a  valve,  which  is  called  the  blow-valve,  or  sometimes  the 
snifting  valve.  Through  this  valve,  the  air  contained  in  the 
cylinder  D,  and  passages  from  it,  is  discharged,  on  the  engine 
being  first  set  in  motion. 

O  the  eduction-pipe,  which  conducts  the  steam  from  the 
valve  I,  to  the  condenser  M. 

P  the  pump  which  supplies  with  water  the  cistern,  or  cold 
w^ell  S  S,  in  which  the  condenser  and  discharging  pump  stand. 

Q  Q  iron  columns  which  support  the  beam.  Of  these  the 
engine  has  four,  although  only  two  are  shown.  They  stand 
upon  one  entire  plate,  seen  edgewise,  on  which  the  principal 
parts  of  the  engine  are  fixed. 

R  R  the  recess  below  the  floor,  for  containing  the  cistern  of 
the  discharging  pump,  condenser,  &:c. 

The  condenser  M,  and  the  air  pump  L,  communicate  by 
means  of  a  horizontal  pipe  containing  a  valve  m,  opening  to- 
wards the  pump ;  the  piston  n  of  this  pump,  also  contains  two 
valves,  and  the  cistern  T,  at  the  top  of  the  pump  cylinder,  con- 
tains other  two  valves,  which,  like  those  of  the  piston  n,  open 
upwards.  When  the  piston  E  of  the  cylinder  is  depressed,  the 
piston  n  of  the  discharging  pump,  it  will  be  obvious  to  inspec- 
tion, will  be  depressed  likewise,  and  its  valves  open,  while  the 


OF  THE  MOVING  FORCES  USED  IN  THE  ARTS.  287 

valve  m  closes ;  hence  the  water  of  the  condensed  steam,  as 
well  as  the  injection  water,  and  any  vapor  or  air  which  may 
be  present,  having  passed  through  the  valve  m,  passes  through 
the  piston  n;  and  when  that  piston  is  drawn  up,  its  valves  close 
and  prevent  their  return,  as  in  common  pump  work.  The 
water  and  air  that  have  thus  got  above  the  piston,  as  the  latter 
rises,  open  the  valves  at  the  bottom  of  the  cistern  T,  in  which 
the  water  remains  till  it  is  full,  but  the  air  passes  into  the  at- 
mosphere. As  the  water  in  the  cistern  T  is  in  a  hot  state,  a 
part  of  it,  for  the  purpose  of  economizing  fuel,  is  pumped  up 
and  returned  to  the  boiler,  the  pump  rod  being  attached  to  the 
great  beam. 

The  steam  constantly  rushing  into  the  condenser  M,  has  a 
perpetual  tendency  to  heat  that  vessel,  as  well  as  the  water  of  the 
cistern  S  S,  in  which  it  stands ;  the  whole  of  the  steam,  if  this 
were  unchecked,  would  not  be  condensed,  or  the  condensation 
would  not  be  sufficiently  rapid,  because  the  injection  water 
itself  flows  out  of  this  cistern.  A  part  of  the  water  is  therefore 
allowed  to  flow  from  this  cistern  by  a  waste  pipe,  and  an  equal 
quantity  of  cold  water  is  constantly  supplied  by  the  pump  P. 

The  cylinder  D,  is  in  many  cases  surrounded  by  a  case,  to 
keep  it  from  being  cooled  too  much  by  contact  whh  the  exter- 
nal atmosphere. 

Expansion  Engines. — The  steam  which  impels  an  engine 
is  always  diminished  in  volume,  by  the  resistance  which  it  has 
to  overcome,  and  tends  naturally  to  occupy  a  larger  space  than 
that  to  which  it  is  confined  while  the  engine  is  at  work.  If  it 
be  dismissed  into  the  air,  or  into  the  condenser,  while  under 
its  greatest  working  pressure,  it  will  not  have  produced  all  the 
useful  effect  which  it  is  capable  of  aflbrding.  If,  on  the  con- 
trary, it  be  separated  and  placed  under  circumstances  where 
it  can  still  expand  further,  before  it  is  dismissed,  this  expansion 
will  be  so  much  additional  gain  to  the  power  of  the  engine. 
Its  general  principles  have  already  been  discussed. 

The  expansive  power  of  steam  may  be  converted  to  use  in 
various  ways,  and  most  of  the  common  forms  of  the  steam 


288  OF  THE  MOVING  FORCES  USED  IN  THE  ARTS. 

engine  may  be  made  to  act  expansively  by  a  proper  arrange- 
ment of  their  valves.  In  Watt's  engine,  this  effect  is  produced 
by  cutting  off  the  steam  from  the  cylinder  before  the  stroke  of 
the  piston  is  completed,  leaving  it  to  the  steam  already  in  the 
cylinder  to  assist  by  its  expansion  in  completing  the  stroke. 
The  steam  in  the  boiler  being  thus  intercepted,  acts  only  at  in- 
tervals. Nevertheless,  its  whole  disposable  force  is  accumulat- 
ed in  the  fly  wheel,  while,  at  the  same  time,  the  force  arising 
from  the  expansion  of  steam  in  the  cylinder,  serves  to  increase 
the  total  amount.  A  great  augmentation  is  thus  produced  in 
the  useful  effect  of  an  engine,  with  the  same  amount  of  fuel, 
and  water. 

Mr  Hornblower,  who  was  one  of  the  first  inventors  of  the 
application  of  expansive  steam,  employed  two  cylinders  having 
their  pistons  connected  to  the  same  beam.  In  the  smaller  of 
these,  the  steam  was  used  at  full  pressure,  after  which  it  was 
discharged  into  the  larger  cylinder,  where  it  again  acted  by  its 
expansive  force.  This  method  affords  a  more  equable  mode 
of  applying  the  expansive  force  of  steam,  than  that  used  by 
Mr  Watt,  but  the  engine  is  more  complex  and  expensive. 

Mr  Woolf  afterwards  adopted  the  plan  of  two  cylinders  with 
the  addition  of  using  his  steam  at  a  high  pressure,  together  with 
a  condenser.  He  appears  to  have  exaggerated  the  expansive 
force  of  steam,  at  high  temperatures,  as  various  other  projec- 
tors have  done.  His  engines,  however,  continue  to  be  used 
and  approved,  in  some  parts  of  England  and  Wales. 

Valves. — The  valves  of  steam  engines  are  shutters,  which 
guard  the  avenues  to  the  boiler  and  condenser,  so  that  by  open- 
ing and  shutting  them,  at  the  required  time,  the  steam  may  be 
made  to  enter,  or  escape,  at  either  end  of  the  cylinder.  Valves 
of  a  great  variety  of  forms,  have  been  used  in  different  en- 
gines, some  of  which  have  a  reciprocating,  others  a  rotary 
motion.  The  puppet  valve  is  a  cone,  or  frustrum  of  a  cone, 
which  is  fitted,  like  a  cover,  to  a  conical  aperture,  which  it 
opens  by  rising,  and  closes  by  falling.  A  valve  of  this  kind  is 
seen  at  V.  in  PI.  IX.    Sliding  valves  are  those  which  do  not 


OF  THE  MOVING  FORCES  USED  IN  THE  ARTS.  289 

rise,  but  slide  on  and  off  of  their  apertures.  Some  of  these 
have  a  cavity  on  their  under  side,  capable  of  connecting  two 
apertures  together,  or  of  forming  a  communication  between 
them,  while  a  third  aperture  is  shut.  This  is  the  case  with 
the  valve  I,  in  PI.  IX.  Rotary  valves  are  usually  constructed 
like  common  stopcocks,  excepting  that  they  command  more 
passages  than  one  at  the  same  time.  If  the  handle  be  placed 
in  one  position,  it  opens  one  passage  while  it  closes  another ;  if 
in  a  different  position,  it  closes  the  first,  and  opens  the  second. 
A  throttle  valve  is  a  partition  turning  on  an  axis,  and  placed 
across  the  interior  of  a  pipe.  If  turned  edgewise,  it  permits 
the  steam  to  pass,  but  if  turned  transversely  it  obstructs  its 
passage.  This  valve  is  commonly  placed  in  the  main  steam 
pipe,  and  connected  with  the  governor  to  regulate  the  quantity 
of  steam  supplied  by  the  boiler.    See  K,  in  PI.  IX. 

On  account  of  the  heat  which  is  kept  up  in  steam  engines, 
the  principal  valves  require  to  be  of  metal,  and  are  fitted  by 
grinding  closely  to  their  seats.  Valves  made  with  leather,  like 
the  common  clack  valve  of  a  pump,  can  only  be  used  about 
the  condenser,  where  the  temperature  is  low,  as  the  valve  m 
PI.  IX. 

Pistons. — As  the  piston  is  liable  to  continual  wear  by  its 
friction  against  the  inside  of  the  cylinder,  it  can  only  be  kept 
sufficiently  tight  by  rendering  its  circumference  elastic.  This 
is  commonly  done  by  winding  it  with  hemp  loosely  twisted. 
The  hemp  packing,  however,  gets  out  of  order  in  time,  and 
requires  to  be  renewed.  To  remedy  this  evil,  various  plans 
have  been  introduced,  for  making  elastic  pistons  of  metal  only. 
The  pistons  invented  by  Cartwright  and  Barton,  consist  of  sev- 
eral parallel  circular  plates  in  close  contact  with  each  other. 
These  are  cut  into  segments,  and  the  segments  pressed  out- 
ward by  steel  springs,  care  being  taken  that  the  fissures  in  the 
different  plates  do  not  coincide.  In  the  piston  of  Jessop,  a 
spiral  coil  of  steel  is  wound  on  the  circumference  of  the  piston, 
which  expands  by  its  own  elasticity,  so  as  to  keep  in  tight  con- 
37 


290  OF  THE  MOVING  FORCES  USED  IN  THE  ARTS, 

tact  with  the  cylinder.  To  increase  the  tightness  and  elasticity 
of  the  piston,  a  hempen  packing  is  placed  within  the  coil. 

Pai'allel  Motion. — A  simple  form  of  a  parallel  motion,  for 
converting  the  rectilinear  motion  of  the  piston  into  the  curvili- 
near one  of  the  beam,  has  already  been  described  on  page  240. 
Another  form  is  shown  in  PI.  IX,  where  the  rod  a  h  turns  upon 
the  joint  a  as  a  fixed  centre,  while  the  rod  c  h  turns  upon  h  as 
/IS  a  centre.  While  the  point  c  would  describe  a  curve  about 
its  centre  6,  the  point  h  describes  an  opposite  curve  about  its 
centre  a.  These  two  curvatures  compensate  each  other,  so 
that  the  point  c  to  which  the  piston  is  attached,  describes  nearly 
a  straight  line. 

The  parallel  motion  was  introduced  by  Mr  Watt,  and  is 
probably  attended  with  less  friction  than  any  other  arrangement 
for  effecting  the  same  object.  It  requires,  however,  to  be  con- 
structed with  great  accuracy.  Various  other  methods  have 
been  applied  to  convert  the  rectilinear,  into  a  curvilinear  move- 
ment. Sometimes  the  piston  is  confined  to  its  path  by  guides, 
or  friction  wheels,  and  connected  to  the  beam  by  a  double 
joint.  In  Newcomen's  engine,  where  the  principal  force  was 
in  the  downward  stroke,  the  piston  was  connected  by  a  chain 
to  an  arched  head  at  the  end  of  the  beam.  In  Cartwright's 
engine,  the  piston  was  attached  to  two  opposite  cranks  which 
were  geared  together,  as  shown  on  page  241.  In  some  of 
Murray's  engines,  the  epicycloidal  movement  was  employed. 
See  page  242.  *  In  Maudslay's  engine,  and  some  others,  in- 
stead of  a  beam,  a  cross  head  is  used,  the  whole  of  which 
moves  up  and  down  in  guides,  instead  of  turning  on  a  centre. 
In  the  vibrating  engines  of  Lester  and  others,  the  cylinder  is 
hung  upon  a  moveable  axis,  and  in  Morey's  engine,  the  cylin- 
der revolves  like  a  fly  wheel,  the  piston  being  made  to  act  on  a 
fixed  crank. 

Historical  Remarks. — The  following  are  some  of  the  most 
interesting  facts  in  the  history  of  the  Steam  Engine. 

*  For  an  account  and  figure  of  an  engine  of  this  kind,  see  Farey  on  the 
Steam  Engine,  p.  686,  and  PI.  XVII. 


OF  THE  MOVING  F0RCF:S  USED  IN  THE  ARTS.  291 

The  ancient  Greeks  and  Romans  appear  to  have  been  ac- 
quainted with  the  power  of  steam  to  produce  motion,  and  in- 
vented the  eoh'pile,  which  was  a  close  vessel  containing  water, 
and  which  gave  out  a  forcible  current  of  steam  whenever  the 
water  was  heated.  The  force  of  this  current  was  used  by 
Hero  to  produce  a  revolving  motion. 

The  power  of  confined  steam,  acting  by  its  pressure,  was 
discovered  by  the  Marquis  of  Worcester,  and  an  account  of  its 
effect  published  by  him  in  1663.  He  produced  a  steam  pow- 
er sufficient  to  burst  a  cannon,  and  constructed  a  machine  ca- 
pable of  raising  water  to  the  height  of  forty  feet.  He  has  not, 
however,  left  any  drawings  or  particular  description  of  his 
machine. 

In  1698,  a  patent  was  granted  to  Thomas  Savery,  for  a 
method  of  raising  water  by  steam.  This  apparatus  consisted 
of  a  boiler,  a  separate  steam  vessel,  and  pipes  commanded  by 
valves.  The  steam  from  the  boiler  was  first  admitted  so  as  to 
fill  the  steam  vessel.  It  was  then  condensed,  and  the  steam 
vessel  filled  with  water  which  rose  by  the  atmospheric  pressure 
from  the  well  or  mine.  The  steam  was  then  readmitted,  and 
the  water  in  the  vessel  was  driven  upward  to  the  top  of  the 
pipes,  and  discharged. 

About  the  year  1705,  Thomas  Newcomen,  constructed  a 
working  steam  engine,  which  has  since  been  called  the  atmos- 
pheric engine.  It  contained  a  cylinder  and  piston,  and  an  al- 
ternating beam,  which  was  applied  to  raise  water  by  working  a 
pump.  The  water  was  condensed  in  the  cylinder  itself,  and 
the  valves  were  moved  by  hand,  until  an  attendant  contrived  to 
make  the  machine  move  its  own  valves,  by  attaching  strings  to 
the  working  beam. 

After  this  the  steam  engine  continued  without  any  important 
alteration,  for  more  than  half  a  century,  when  about  1769,  the 
discoveries  and  inventions  of  James  Watt,  gave  a  new  spring  to 
the  energies  of  this  machine,  and  have  more  than  doubled  the 
power  which  it  formerly  possessed.  Mr  Watt's  improvements 
were  numerous  and  important,  but  those  of  greatest  value  were 


292  OF  THE  MOVING  FORCES  USED  IN  THE  ARTS. 

the  following.  1.  He  introduced  the  separate  condenser.  2. 
He  applied  the  double  action  of  steam  by  closing  the  top  of  the 
cylinder,  and  admitting  the  steam  alternately  at  each  end.  3. 
He  converted  to  use  the  expansive  power  of  steam,  by  cutting 
off  the  current  before  the  end  of  the  stroke.  Mr  Watt  also  in- 
vented the  principle  of  the  parallel  motion,  and  applied  the 
governor  to  regulate  the  supply  of  steam. 

In  1802,  the  first  high  pressure  or  noncondensing  engines 
were  constructed  by  Oliver  Evans,  in  Philadelphia,  and  in  the 
same  year  by  Trevithick  and  Vivian,  in  England.  The  idea 
of  such  an  engine  had  before  occurred  to  Leupold,  Watt,  and 
others.  The  first  steam  carriage  was  put  in  motion  on  a  rail- 
way, by  Trevithick  and  Vivian,  in  1805. 

Steam  navigation  was  suggested  in  England  by  Jonathan 
Hulls,  in  1736.  It  was  first  tried  in  practice  by  the  Marquis 
de  JoufFroy  in  France,  in  1782,  and  nearly  at  the  same  time 
in  America,  by  James  Rumsey  of  Virginia,  and  John  Fitch  of 
Philadelphia.  It  was  first  made  practically  successful  by  Rob- 
ert Fulton,  at  New  York,  in  1807.  The  first  steam  vessel 
which  crossed  the  Atlantic,  was  the  American  ship  Savannah, 
in  1819. 

Projected  Improvements, — Besides  the  improvements  which 
have  been  actually  effected  in  the  construction  and  application 
of  the  steam  engine,  a  variety  of  projects  for  increasing  the 
power  and  usefulness  of  this  agent,  have  from  time  to  time  occu- 
pied the  attention  of  ingenious  men.  Of  the  improvements 
which  have  been  attempted,  some  are  opposed  by  obstacles 
which  have  not  yet  been  satisfactorily  surmounted,  and  others 
by  difficulties  in  themselves  insurmountable.  The  following 
have  been  among  the  most  prominent  subjects  of  speculation. 

1.  Rotative  Engines. — These  are  engines  in  which  the 
steam  is  so  applied  as  to  produce  a  direct  rotary  motion  with- 
out the  intervention  of  a  rectilinear  movement.  Engines  on 
this  principle  have  been  constructed  in  many  different  ways. 
An  idea  of  one  of  the  most  obvious  forms  may  be  obtained  from 
the  excentric  pumps  described  in  the  following  Chapter,  which 


OF  THE  MOVING  FORCES  USED  IN  THE  ARTS. 


293 


have  been  converted  into  steam  engines,  by  reversing  the  mo- 
tions, and  changing  the  resistance  for  the  power.  Some  rota- 
tive engines  have  been  constructed  on  the  principle  of  Barker's 
mill ;  others  have  been  made  by  immersing  an  overshot  wheel 
in  a  cistern  of  heated  fluid,  either  water,  oil,  or  melted  metal, 
and  delivering  the  steam  under  the  ascending  or  inverted  buck- 
ets, so  that  when  these  were  filled  with  steam,  the  full  buckets 
on  the  opposite  side  might  preponderate  and  cause  the  wheel 
to  revolve.  But  in  general  the  rotary  engines  hitherto  con- 
structed, have  either  been  feeble  in  power,  or  encumbered  with 
excessive  friction,  on  account  of  the  extensive  packing  which 
is  necessary  to  keep  them  tight ;  so  that  none  of  them  have 
found  their  way  into  use.  It  is  probable  that  no  method  of 
constructing  a  variable  cavity  for  steam,  which  is  in  other  re- 
spects suitable,  affords  so  advantageous  a  mode  of  applying 
the  power,  as  the  cylinder  and  piston  producing  rectilinear 
motion. 

Use  of  Steam  at  high  Temperatures, — ^In  noncondensing  or 
high  pressure  engines,  the  power  which  is  convertible  to  use, 
consists  of  the  surplus  which  remains,  after  overcoming  the 
pressure  of  the  atmosphere.  Of  course  the  higher  is  the  tem- 
perature at  which  the  steam  is  worked,  the  greater  is  the  total 
gain,  supposing  the  absorption  of  heat  and  the  production  of 
power  to  continue  to  take  place  in  equal  proportions.  This 
consideration,  with  other  expected  advantages,  has  given  rise  to 
many  attempts  to  improve  the  steam  engine,  by  devising  modes 
of  applying  steam  at  much  higher  temperatures  than  those 
which  it  has  been  ordinarily  found  practicable  to  employ.  At- 
tempts of  this  kind  have  also  frequently  been  founded  upon  an 
undue  estimate  of  the  elastic  force  of  steam  at  high  tempera- 
tures, and  of  the  absorption  of  heat  during  its  production.  In 
practice,  it  is  found  difficult  to  obtain  a  material  capable  of 
confining  water  and  steam  in  safety,  when  raised  to  such  a  tem- 
perature as  to  produce  a  pressure  of  ten  or  more  atmospheres ; 
since,  independently  of  the  strain  upon  the  joinings,  the  cohesive 
strength  of  metals  is  diminished,  and  their  oxidation  promoted, 
by  exposure  to  great  heat. 


^94  OF  THE  MOVING  FORCES  USED  IN  THE  ARTS. 

Use  of  Vapors  of  low  Temperature. — Certain  liquids  such 
as  alcohol,  ether,  sulphuret  of  carbon,  and  a  liquid  obtained  by 
condensing  oil  gas,  have  been  proposed  as  substitutes  for  water, 
in  producing  steam,  on  account  of  the  low  temperature  at 
which  they  are  converted  into  vapor.  Thus  alcohol  boils  at 
about  173  degrees  of  Fahrenheit,  sulphuric  ether  at  98  degrees, 
muriatic  ether  at  51  degrees,  *  sulphuret  of- carbon  at  116  de- 
grees, and  oil  gas,  liquid,  at  186  ;  all  of  which  are  lower  than 
the  boiling  point  of  water.  Some  of  these,  when  raised  to 
the  boiling  point  of  water,  have  a  much  greater  elastic  force 
than  that  fluid.  Thus  the  sulphuret  of  carbon  at  212  degrees, 
has  an  elastic  force  equal  to  about  four  atmospheres,  f  and 
sulphuric  ether  of  nearly  six  atmospheres.  But  these  advan- 
tages are  nearly  counterbalanced  by  the  small  spaces  through 
which  these  vapors  act,  their  volume  at  their  boiling  point,  be- 
ing only  from  about  an  eighth  to  a  third  part  of  that  of  steam, 
at  the  boiling  point  of  water.  To  this  disadvantage  may  be 
added  the  expensive  character  of  these  substances,  and  the 
difficulty  of  condensing  them  without  loss,  in  any  working  en- 
gine. Some  of  them  likewise,  as  the  ethers,  act  chemically 
upon  metals,  and  could  not  on  this  account  be  employed  in  en- 
gines made  of  the  common  materials. 

Gas  Engines. — It  has  been  attempted  to  obtain  power  for 
propelling  machinery,  from  the  combustion,  or  explosion,  of 
inflammable  elastic  fluids,  such  as  coal  gas,  and  the  vapor  of 
combustible  liquids,  mixed  with  atmospheric  air.  In  combus- 
tions of  this  kind,  rarefaction  and  subsequent  condensation 
take  place,  which  if  conducted  within  suitable  cavities,  may 
be  made  to  afford  a  moving  power,  applicable  to  machinery. 
The  principal  engines  which  have  been  constructed  for  using 
this  power,  are  those  of  Messrs  Morey,  in  this  country,  and 
Brown,  in  England.  If  a  power  of  this  kind  could  be  made 
to  afford  an  adequate  propelling  force  for  locomotive  engines 
«pon  public  roads,  it  would  possess  an  advantage  in  the 

*  lire's  Dictionary. 

I  See  Tredgold's  tables,  Steam  Engine,  p.  78—81. 


OF  THE  MOVING  FORCES  USED  IN  THE  ARTS.  295 

lightness  of  the  machinery,  compared  with  the  weight  of  steam 
engines  with  their  water  and  fuel.  But  it  remains  for  experi- 
ence to  determine,  whether  the  space  through  which  the  force 
will  act,  taken  in  connexion  with  the  cost  of  the  materials,  can 
render  this  an  economical  source  of  power. 

In  addition  to  the  foregoing  method  of  procuring  power  by 
the  combustion  of  gases.  Sir  H.  Davy  has  proposed  the  em- 
ployment of  certain  fluids  which  are  volatile  at  common  tem- 
peratures, but  which  have  been  condensed  into  liquids  under 
great  pressure,  such  as  carbonic  acid,  ammonia,  he.  His 
views  are  founded  upon  the  immense  difference  which  exists 
between  the  increase  of  elastic  force  in  gases  under  high,  and 
low  temperatures,  hy  similar  increments  of  temperature.  But 
doubts  have  been  raised  upon  this  subject,  with  regard  to  the 
space  through  which  the  force  of  these  gases  will  act,  and  also 
in  regard  to  the  quantity  of  heat  required  to  produce  the  change 
of  temperature  required.'^ 

Steam  Carriages. — It  has  long  been  a  favorite  object  with 
projectors  to  construct  a  form  of  the  steam  engine  in  connexion 
with  a  carriage,  which  should  be  capable  of  propelling  itself 
upon  the  public  roads.  Locomotive  engines  are  capable  of 
moving  themselves  upon  rail  roads,  and  of  drawing  with  them 
additional  loaded  carriages ;  because  in  this  case  the  motion  is 
uniform,  and  very  little  of  the  power  is  expended  in  surmounting 
obstacles,  or  changing  the  form  of  the  road.  But  upon  a  public 
highway  it  requires,  by  a  common  estimate,  about  eight  times 
as  much  power  to  propel  a  carriage,  as  it  does  upon  a  rail  road. 
Of  course  the  weight  and  inertia  of  an  engine  capable  of  pro- 
ducing this  power,  must  increase  somewhat  in  the  same  pro- 
portion, and  a  great  part  of  the  power  will  become  necessary 
to  transport  the  machine  itself.  The  inertia,  also,  will  be  con- 
tinually brought  into  unfavorable  action  by  the  jolts  and  con- 
cussions inseparable  from  highway  travelling,  and  thus  endanger 
the  destruction  of  a  machine  requiring  such  nice  adaptation 


Philosophical  Transactions,  1826,  Tredgold  on  the  Steam  Engine,  p.  84. 


296         OF  THE  MOVING  FORCES  USED  IN  THE  ARTS. 

of  parts  as  the  steam  engine.  It  appears  that  steam  carriages 
have  been  made  to  run  upon  good  roads,  during  short  experi- 
ments, while  the  engine  was  new.  But  we  have  no  account,  as 
yet,  of  any  one  having  long  performed  this  kind  of  service. 

Steam  Gun. — Mr  J.  Perkins,*  whose  experiments  on  the 
steam  engine  are  well  known,  has  attempted  the  employment 
of  the  expansive  force  of  steam,  as  a  substitute  for  gunpow- 
der, in  throwing  projectiles.  The  steam  gun  invented  by  him, 
is  somewhat  similar  in  its  construction  to  the  air  gun,  but  the 
power  is  derived  from  a  magazine  of  water  heated  to  a  very 
high  temperature,  so  that  when  portions  of  it  are  discharged 
from  the  vessel  containing  it,  they  produce  steam  enough  to 
project  a  cannon  ball  with  great  force.  The  balls  are  admitted 
into  the  gun,  in  succession,  from  a  hopper,  and  can  be  dis- 
charged at  the  rate  of  24  in  a  minute.  It  appears  from  some 
experiments  made  with  these  guns  in  France,  that  the  projec- 
tile force  of  steam  is  greatly  inferior  to  that  of  gunpowder, 
a  consequence,  no  doubt,  of  the  vast  difference  which  is  known 
to  exist  in  the  initial  force  of  the  two  agents  ;  nevertheless,  the 
rapidity  with  which  the  discharges  may  be  made,  seems  capa- 
ble of  advantageous  employment  in  some  situations. 

GUNPOWDER. 

Manufacture. — Gunpowder  is  a  solid  explosive  mixture 
composed  of  nitre,  sulphur,  and  charcoal,  reduced  to  powder, 
and  mixed  intimately  with  each  other.  The  proportion  of  the 
ingredients  varies  very  considerably ;  but  good  gunpowder  may 
be  composed  of  the  following  proportions ; — 76  parts  of  nitre, 
15  charcoal,  and  9  sulphur,  equal  to  100.  These  ingredients 
are  first  reduced  to  a  fine  powder  separately,  then  mixed  in- 
timately, and  formed  into  a  thick  paste.  This  is  done  by 
pounding  them  for  a  long  time  in  wooden  mortars,  at  the  same 
time  moistening  them  with  water,  to  prevent  the  danger  of 

*  The  public  are  indebted  to  Mr  Perkins  for  the  art  of  steel  engraving,  the 
nail  machine,  and  many  other  useful  inventions. 


OF  THE  MOVING  FORCES  USED  IN  THE  ARTS. 


297 


explosion.  The  more  intimate  is  the  mixture,  the  better  is  the 
powder,  for  since  nitre  does  not  detonate,  except  when  in  con- 
tact with  inflammable  matter,  the  whole  detonation  will  be  more 
speedy,  the  more  numerous  the  surfaces  in  contact.  After  the 
paste  has  dried  a  little,  it  is  placed  upon  a  kind  of  seive  full 
of  small  holes,  through  which  it  is  forced.  By  that  process  it 
is  divided  into  grains,  the  size  of  which  depends  upon  the  size 
of  the  holes  through  which  they  have  passed. 

The  powder  when  dry,  is  put  into  barrels,  which  are  made 
to  turn  round  on  their  axis.  By  this  motion  the  grains  of  gun- 
powder rub  against  each  other,  their  asperities  are  worn  off, 
and  their  surfaces  are  made  smooth,  the  powder  is  then  said  to 
be  glazed.  The  granulation  and  glazing  of  the  powder  causes 
it  to  explode  more  quickly,  perhaps  by  facilitating  the  passage 
of  the  flame  among  the  particles. 

Detonation. — When  gunpowder  comes  in  contact  w^ith  any 
ignited  substance,  it  explodes,  as  is  well  known,  with  great 
violence.  This  effect  may  take  place  even  in  a  vacuum.  A 
vast  quantity  of  gas  or  elastic  fluid  is  emitted,  the  sudden  pro- 
duction of  which,  at  a  high  temperature,  is  the  cause  of  the 
violent  effects  which  this  substance  produces.  The  combus- 
tion is  evidently  owing  to  the  decomposition  of  the  nitre  by  the 
charcoal  and  sulphur.  The  products  are  carbonic  oxide,  car- 
bonic acid,  nitrogen,  sulphurous  acid,  and  probably  sulphuret- 
ed  hydrogen.  Mr  Cruikshanks  has  ascertained  that  no  per- 
ceptible quantity  of  water  is  formed.  What  remains  after  the 
combustion,  is  potash  combined  with  a  small  portion  of  carbon- 
ic acid,  sulphate  of  potash,  a  very  small  proportion  of  sul})huret 
of  potash,  and  unconsumed  charcoal. 

Force. — The  elastic  fluid  which  is  generated,  when  gunpow- 
der is  fired,  being  very  dense,  and  much  heated,  begins  to  ex- 
pand with  a  force  at  least  1000  times  greateV  than  that  of  air 
under  the  ordinary  pressure  of  the  atmosphere.  And  allowing 
the  pressure  of  the  atmosphere  to  be  i4J  pounds  upon  every 
square  inch,  the  initial  force,  or  pressure,  of  fired  gunpowder 
will  be  equal  to  at  least  14,750  pounds  upon  every  square  inch 
38 


298  OF  THE  MOVING  FORCES  USED  IN  THE  ARTS. 

of  the  surface  whicli  confines  it.  But  this  estimate,  which  is 
that  of  Mr  Robins,  is  one  of  the  smallest  which  have  been 
made.  According  to  Bernoulli,  the  initial  elasticity  with  which 
a  cannon  ball  is  impelled,  is  at  least  equal  to  10,000  times  the 
pressure  of  the  atmosphere,  and  from  Count  Rumford's  exper- 
iments it  appears  more  than  three  times  greater  than  this. 

Gunpowder  on  account  of  its  expensiveness,  and  the  sud- 
denness and  violence  of  its  action,  is  not  employed  as  a  reg- 
ular moving  force  for  machinery.  It  is  chiefly  applied  to  the 
throwing  of  shot  and  other  projectiles,  and  the  blasting  of  rocks. 

When  a  ball  is  thrown  from  a  gun,  the  greatest  force  is  ap- 
plied to  it  by  each  particle  at  the  moment  of  its  explosion. 
But  since  the  ball  cannot  at  once  acquire  the  same  velocity 
with  which  the  elastic  fluid  if  at  liberty  would  expand,  it  con- 
tinues to  be  acted  upon  by  the  fluid,  and  its  motion  is  acceler- 
ated in  common  cases,  until  it  has  escaped  from  the  mouth  of 
the  piece.  The  accelerating  force,  however,  is  not  uniform, 
and  hence  the  following  circumstances  deserve  attention.  1. 
The  elasticity  is  inversely  as  the  space  which  the  fluid  occu- 
pies, and,  therefore,  as  it  forces  the  ball  out  of  the  gun,  it  con- 
tinually diminishes.  2.  The  elasticity  would  diminish  in  this 
ratio,  even  if  the  temperature  remained  the  same ;  but  it  must 
diminish  in  a  much  greater  ratio,  because  a  reduction  of  tem- 
perature takes  place,  both  from  the  dispersion  of  the  heat,  and 
the  absorption  of  it  by  the  fluid  itself,  during  its  rarefaction.  3. 
The  fluid  propels  the  ball  by  following  it,  and  acts  with  a  force 
that  is,  cetcerus  paribus,  proportionate  to  the  excess  of  its  ve- 
locity above  the  velocity  of  the  ball.  The  greater  the  velocity 
that  the  ball  has  acquired,  the  less,  therefore,  is  its  momentary 
acceleration.  4.  From  this  change  of  relative  velocity,  there 
must  be  a  period,  when  the  velocity  of  the  ball  will  exceed 
that  of  the  elastic  fluid,  and  therefore  the  proper  length  for  a 
gun  must  be  that,  in  which  ihe  ball  would  leave  the  mouth,  at 
the  time  when  the  velocities  are  equal ;  and  all  additional  length 
of  the  piece  beyond  this,  can  only  serve  to  retard  the  ball, 
both  by  friction  and  atmospheric  pressure. 


OF  THE  MOVING  FORCES  USED  IN  THE  ARTS.  299 

The  force  of  fired  gunpowder  is  found  to  be  very  nearly- 
proportionate  to  the  quantity  employed ;  so  that  if  we  nej^lect 
to  consider  the  resistance  of  the  atmosphere,  then  the  height 
to  which  the  ball  will  rise,  and  its  greatest  horizontal  range, 
must  be  directly  as  the  quantity  of  powder,  and  inversely  as 
the  weight  of  the  ball.  Count  Rumford,  however,  found  that 
the  same  quantity  of  powder  exerted  somewhat  more  force 
upon  a  large  ball,  than  on  a  smaller  one. 

Properties  of  a  Gun. — The  essential  properties  of  a  gun, 
are  to  confine  the  elastic  fluid  as  completely  as  possible, 
and  to  direct  the  course  of  the  ball  to  a  rectilinear  path  ; 
and  hence  arises  the  necessity  of  an  accurate  bore.  The 
windage,  or  space  produced  by  the  difference  of  diameter 
between  the  ball  and  the  bore,  greatly  diminishes  the  effect  of 
the  powder,  by  allowing  a  part  of  the  elastic  fluid  to  escape 
before  the  ball.  The  advantage  of  a  rifle  barrel  is  chiefly  de- 
rived from  the  more  accurate  contact  of  the  ball  with  its  cavity. 
When  the  bore  is  twisted,  it  is  also  supposed  to  produce  a  ro- 
tation of  the  ball  round  an  axis,  in  the  direction  of  its  motion, 
which  renders  it  less  liable  to  deviate  from  its  path  on  account 
of  irregularities  in  the  resistance  of  the  air.  The  usual  charge 
of  powder  is  one  fifth,  or  one  sixth  of  the  weight  of  the  ball ; 
and  for  battering,  one  third.  When  a  twenty  four  pounder  is 
fired  with  two  thirds  of  its  weight  of  powder,  it  may  be  thrown 
about  four  miles,  the  distance  being  reduced  by  the  resistance 
of  the  air,  to  about  one  fifth  of  that,  which  it  would  describe  if 
thrown  in  a  vacuum.  * 

It  is  certain  that  the  grains  of  gunpowder  do  not  inflame  at 
once,  but  that  the  inflammation  occupies  time  in  being  commu- 
nicated from  one  particle  to  another,  so  that  they  act  success- 
ively, rather  than  simultaneously,  in  impelling  the  ball.  This 
circumstance  contributes  greatly  to  the  safety  of  fire  arms,  for 
if  the  whole  charge  of  powder  exploded  at  once,  the  piece 
would  be  in  danger  of  bursting  before  the  inertia  of  the  ball 


"  Young's  Natural  Philosophy,  vol.  i.  p.  350. 


300  OF  THE  MOVING  FORCES  USED  IN  THE  ARTS. 

would  be  overcome.  It  is  on  account  of  the  suddenness  of- 
their  detonation,  that  the  various  fulminating  powders  are  inap- 
plicable to  use  in  fire  arms.  The  bursting  of  a  gun  may  be 
occasioned  by  the  defective  condition  of  the  metal,  the  dispro- 
portionate amount  of  the  charge,  the  adhesion  andjnertia  of 
the  shot,  or  the  inertia  of  some  other  body  opposing  the  escape 
of  the  charge.  It  is  from  this  last  circumstance  that  a  gun  is 
liable  to  burst,  if  fired  with  its  muzzle  under  water. 

To  enable  gunpowder  to  exert  its  full  effect,  the  proportions 
of  the  cavity  of  the  piece,  to  the  charge,  should  be  such,  as  to 
allow  all  the  grains  to  explode  before  they  leave  the  cavity ; 
and  also  to  permit  the  elastic  fluid  to  expend  as  much  of  its 
pressure  as  is  capable  of  accelerating  the  ball.  The  superiori- 
ty of  a  musket  over  a  pistol,  arises  from  its  prolonging  the  ac- 
tion of  the  powder  in  this  way.  But  for  reasons  already  stat- 
ed, there  are  limits  to  the  length  of  the  barrel,  which  cannot 
be  usefully  exceeded,  and  these  have  been  nearly  settled  by 
common  practice. 

Blasting. — The  splitting  of  rocks  by  gunpowder  is  perform- 
ed by  drilling  holes  to  a  certain  depth,  and  inserting  a  charge 
of  powder  at  the  bottom.  The  hole  is  then  filled  up  by  ram- 
ming in  fragments  of  stone,  bricks,  or  other  hard  substances, 
keeping  in  a  steel  wire,  which  is  afterwards  withdrawn  to  fur- 
nish a  passage  for  the  priming  by  which  fire  is  communicated 
to  the  charge.  To  prevent  the  danger  of  a  spark,  copper  wire 
is  often  used  instead  of  steel.  And  to  prevent  the  small  frag- 
ments from  flying  about,  it  is  found  useful  to  cover  the  rocks 
with  brush  wood,  or  some  other  elastic  substance. 

Rocks  may  be  blasted  at  a  considerable  depth  under  water, 
by  means  of  the  diving  bell,  which  enables  workmen  to  drill 
and  charge  them  in  safety.  In  the  method  practised  at  Howth, 
in  Ireland,  after  the  charge  is  inserted,  a  tin  tube  is  carried  up 
from  the  rock  to  the  surface  of  the  water.  It  is  kept  empty 
and  made  water  tight  by  screwing  the  joints  to  each  other  as 
the  bell  ascends.  The  powder  is  ignited  by  dropping  pieces 
of  red  hot  iron  through  the  tube,  from  a  boat  at  the  surface. 


OF  THE  MOVING  FORCES  USED  IN  THE  ARTS. 


301 


When  the  depth  exceeds  twelve  feet,  no  danger  or  inconve- 
nience is  experienced  by  the  boats,  beyond  a  violent  eruptive 
ebullition  of  the  water. 


Smeaton's  Miscellaneous  papers,  4to.  1814 ; — Robison's  Mechani- 
cal Philosophy,  vol.  ii.  and  iii. ; — Gregory's  Mechanics; — Brew- 
ster's Ferguson's  Mechanics; — Nicholson's  Operative  Mechanic, 
8vo. ; — Farey's  Treatise  on  the  Steam  Engine,  4to.  1827;  this  is  the 
most  extensive  work  on  its  subject ; — Tredgold  on  the  Steam  En- 
gine, 4to.  1828;  this  is  the  most  philosophic  work  on  the  subject; — 
Stuart  on  the  Steam  Engine,  8vo.  1824; — Partingdon  on  the  Steam 
Engine,  8vo.  1825; — Bossut  Traiti  Theoretiqiie  et  Experimental  rf' 
Hydrodynamique,  1771 ; — Du  Boat  Traite  Hydraulique,  &c.  1786, 
&c.; — Playfair's  Outlines  of  Natural  Philosophy,  8vo.  1819  ; — Ure's 
Dictionary  of  Chemistry; — Works  of  Coulomb,  Desaguliers,  De 
La  Hire,  Deparcieux,  Hutton,  Robins,  Rumford,  &c. 


CHAPTER  XIII. 

ARTS  OF  CONVEYING  WATER. 

The  employment  of  water  as  an  agent  for  producing  motion, 
has  already  been  considered.  It  remains  to  attend  to  the  va- 
rious modes  by  which  this  fluid  may  be  conveyed  from  one 
place  to  another,  either  for  use  in  the  arts,  or  for  application  to 
the  necessary  purposes  of  life.  The  principal  circumstances 
which  require  attention  under  this  head  are  the  following.  1. 
The  conducting  of  water  from  one  place  to  another  having  the 
same,  or  a  lower,  level.  2.  The  raising  of  water  to  a  higher 
kvel.    3.  The  projection  of  water  through  the  atmosphere. 

OF  CONDUCTING  WATER. 

Aqueducts. — When  water  flows  in  a  current  or  stream,  as  in 
rivers  or  canals,  it  does  so  in  obedience  to  gravitation,  and  in 
consequence  of  the  surface  being  lower  at  the  end  towards 
which  it  is  flowing,  than  in  that  from  which  it  proceeds.  Its 
motions  are  governed  by  laws  somewhat  different  from  those  of 
solid  bodies  descending  upon  inclined  planes,  and  this  differ- 
ence is  owing  to  the  want  of  cohesion  among  the  particles. 
Instead  of  moving  simultaneously,  the  particles  continually 
change  their  relative  position,  so  that  while  one  portion  of  the 
fluid  may  be  moving  rapidly,  another  may  be  stationary,  or 
even  moving  by  an  eddy  in  a  contrary  direction.  The  motion, 
however,  will  continue  both  in  open  channels,  and  in  properly 
constructed  pipes,  until  an  equilibrium  is  produced,  by  the  sur- 
face at  both  ends  of  the  channel,  arriving  at  the  same  level. 
Aqueducts  are  artificial  channels  or  conduits  for  the  convey- 
aace  of  water  in  a  horizontal  or  descending  direction.  The 


ARTS  OF  CONVEYING  WATER. 


303 


aqueducts  constructed  by  the  ancient  Romans,  were  among 
the  most  costly  monuments  of  their  arts.  Several  of  these 
were  from  thirty  to  a  hundred  miles  in  length,  and  consisted  of 
vast  covered  canals  built  of  stone.  They  were  carried  over 
valleys  and  level  tracts  of  country  upon  arcades,  which  were 
sometimes  of  stupendous  height  and  solidity.  A  similar  meth- 
od has  been  practised  in  some  modern  cities  of  warm  or  tem- 
perate climates. 

In  colder  latitudes,  if  the  course  of  the  aqueduct  is  above 
the  ground,  the  water  is  liable  to  be  interrupted  by  freezing  in 
winter.  It  has  therefore  become  common  to  resort  to  subter- 
ranean passages  for  water,  which  are  placed  so  deep  as  to  be 
below  the  reach  of  frost,  and  are,  also,  favorably  situated  both 
for  convenience  and  economy.  Culverts  and  drains  which  are 
intended  merely  to  remove  and  expend  water,  are  usually  made 
of  brick  or  stone ;  but  for  conveying  water  with  the  smallest 
expenditure  by  loss,  water  pipes  are  most  frequently  resorted 
to. 

Water  Pipes. — The  pipes  by  which  water  is  conveyed  be- 
neath the  ground,  are  generally  of  small  or  moderate  size,  and 
are  intended  to  be  water  tight.  In  consequence  of  a  well 
known  law  of  fluids,  a  water  pipe  may  possess  any  degree  of 
flexure,  and  any  number  of  curvatures  below  the  level  of  the 
fountain  head  ;  yet  if  it  be  not  obstructed  by  air,  or  any  other 
internal  obstacle,  it  will  rise  at  the  discharging  end,  and  may 
be  delivered  at  the  height  of  the  original  level.*  Pipes  for 
transmitting  water  have  been  made  from  a  great  variety  of 
materials.  It  is  desirable  that  they  should  possess  strength, 
tightness,  and  durability,  and  that  the  material  of  which  they 
are  composed,  should  not  be  capable  of  contaminating  the 
water.  Wooden  pipes  are  commonly  hollow  logs,  perforated 
by  boring  through  their  axis,  and  connected  together  by  making 
the  end  of  one  log  conical,  and  inserting  it  into  a  conical  cavi- 

*  It  appears  that  the  use  of  water  pipes  was  not  unknown  to  the  ancients. 
Some  rules  respecting  the  use  of  leaden  and  earthen  pipes  are  given  by 
Vitruvius,  de  Architectura,  Lib.  viii. 


304 


ARTS  OF  CONVEYING  WATER. 


ty  in  the  next.  When  large  trunks  are  required,  they  are  com- 
posed of  thick  staves,  and  hoops,  h'ke  a  cask.  They  should, 
where  practicable,  be  imbedded  in  clay,  and  buried  at  a  greater 
depth  than  the  frost  is  ever  known  to  penetrate.  Wooden 
pipes,  are  in  common  use  in  this  country,  but  are  liable  to 
decay,  especially  at  the  joints,  where  their  thickness  is  smallest. 
In  salt  marshes  they  are  more  durable,  though  still  liable  to  de- 
cay from  the  attrition  and  decomposing  effect  of  the  water 
within  them. 

Iron  pipes  are  at  the  present  day,  considered  preferable  to 
those  of  wood,  being  stronger  and  in  most  situations  more  dur- 
able. They  are  made  of  cast  iron,  with  a  socket,  or  enlarged 
cavity  at  one  end,  into  which  the  end  of  the  next  pipe  is  re- 
ceived. The  joints  thus  formed  are  rendered  tight,  either  by 
filling  the  interstices  with  lead,  or  by  driving  in  a  small  quantity 
of  hemp,  and  filling  the  remainder  of  the  socket  with  iron  ce- 
ment, made  of  sulphur,  muriate  of  ammonia,  and  chippings  of 
iron.  Copper  pipes  are  extremely  durable,  and  are  made  of 
sheet  copper,  with  the  edge  turned  up  and  soldered.  They 
require  to  be  tinned  inside,  on  account  of  the  poisonous  char- 
acter of  some  of  the  compounds,  which  are  liable  to  be  formed 
in  them.  Lead  pipes  are  much  employed  for  small  aqueducts, 
owing  to  the  facility  with  which  they  can  be  soldered,  and  bent 
in  any  direction.  They  are  commonly  cast  in  short  pieces, 
and  afterwards  elongated  by  drawing  them  through  holes,  in 
the  same  manner  as  wire.  Leaden  pipes,  in  general,  are  sup- 
posed not  to  contaminate  the  water  contained  in  them,  because 
the  carbonate  of  lead,  which  is  sometimes  formed  in  them,  is 
insoluble  in  water.  They  are  not  safe,  however,  for  pumps 
and  pipes  intended  to  convey  acid  liquors.  Stone  pipes  pre- 
serve the  water  contained  by  them  in  a  very  pure  state.  They 
are,  however,  expensive,  on  account  of  the  labor  of  working 
them,  v/ith  the  exception  of  soap  stone,  which,  being  easily 
shaped  and  bored,  may  be  usefully  applied  to  the  purpose  of 
conveying  water,  in  those  places  where  it  is  easily  procured. 
Earthen  pipes  made  of  common  pottery  ware  and  glazed  on 


I 


ARTS  OF  CONVEYING  WATER.  305 

the  inside,  are  sometimes  used,  but  are  more  liable  to  be  brok- 
en than  most  of  the  other  kinds. 

Friction  of  Pipes. — In  a  river,  or  open  channel,  it  is  observ- 
able that  the  water  flows  most  rapidly  in  the  middle  of  the 
upper  surface,  while  it  is  most  retarded  at  the  edges,  and  at 
the  bottom.  In  like  manner  in  a  cylindrical  pipe,  the  fluid  has 
the  greatest  velocity  at  the  centre,  or  axis,  and  the  smallest  ve- 
locity at  the  surface,  or  where  it  is  in  contact  with  the  pipe. 
The  force  by  which  this  retardation  is  occasioned,  is  common- 
ly called  friction.  It  differs  in  many  respects  from  the  friction 
of  solids,  and  more  resistance  is  occasioned  by  the  internal 
action  of  the  fluid  particles  upon  each  other,  than  by  the  con- 
tact of  the  solid  surface  in  which  they  are  contained.  The 
investigation  of  the  laws  which  govern  the  movements  of  fluids 
is  intricate,  and  the  results  of  experiment  have  not  agreed 
with  the  previous  conclusions  of  theory.  Various  writers  on 
the  science  of  hydraulics  have  treated  this  subject  with  an  ex- 
tensiveness  of  research,  which  can  only  be  understood  from 
their  own  works.  Among  the  more  simple  practical  facts,  to 
which  it  is  useful  to  attend,  the  following  may  be  briefly  stated. 

1.  The  velocity  of  water  is  greater  in  a  large  pipe  than  in  a 
small  one  having  the  same  position,  and  hence  a  large  pipe 
will  discharge  more  water  in  a  given  time,  than  a  number  of 
small  ones  having  jointly  the  same  capacity.  A  pipe  of  two 
inches  diameter  will  give  more  water  than  five  pipes  of  one 
inch  diameter;  it  being  ascertained  that  the  squares  of  the  dis- 
charges are  very  nearly  as  the  fifth  powers  of  the  diameters.  * 

2.  Irregularities  and  inequalities  in  the  diameter  of  the  pipe, 
diminish  the  amount  of  water  which  they  transmit,  by  altering 
the  direction  of  the  particles,  and  by  changing  their  velocity,  so 
as  to  renew  the  resistance  of  inertia.  3.  In  like  manner  all 
curves  and  angles,  which  occur  in  the  pipe,  have  a  similar  retard- 
ing effect,  by  creating  new  motions  or  counter  currents.  4.  The 
form  of  the  end  of  the  pipe  which  communicates  with  the  foun- 
tain head,  or  reservoir,  greatly  affects  the  quantity  of  water  re- 

*Robison's  Mechanical  Philosopl)y,  vol.  ii.  p.  578. 
39 


30G 


ARTS  OP  CONVEYING  WATER. 


ceived  by  it.  If  it  be  gradually  enlarged  like  a  trumpet  mouth, 
a  larger  quantity  of  water  will  be  received  than  by  any  of  the 
modes  vvhich  follow,  because  the  direction  given  to  the  particles 
by  this  form,  is  most  favorable  to  their  admission.  If  die  en- 
trance  to  the  pipe  be  abrupt,  in  consequence  of  the  cavity  be- 
ing wholly  cylindrical,  the  particles  will  have  a  tendency  to 
cross  each  other,  and  less  water  will  enter  the  pipe  in  a  given 
time.  And  if  the  end  of  the  pipe  projects  into  the  reservoir,, 
a  variety  of  opposing  forces  will  be  produced  among  the  parti- 
cles moving  toward  the  entrance,  so  that  a  smaller  quantity 
will  be  received  by  the  pipe,  than  in  either  of  the  preceding 
cases. 

The  form  of  the  discharging  orifice  also  influences  the  quan- 
tity of  water  delivered  by  a  pipe  in  a  given  time.  If  the  end 
of  the  pipe  be  enlarged,  by  adding  to  it  a  frustum  of  a  hollow 
cone,  the  amount  of  water  discharged  in  some  cases,  may  be 
prodigiously  increased.  *  This  fact,  described  by  Venturi,  ap- 
pears to  be  the  result  of  the  pressure  of  the  atmosphere,  aided 
by  the  inertia  and  cohesiveness  of  the  water. 

Obstruction  of  Pipes. — Water  pipes  are  liable  to  be  ob- 
structed, chiefly  by  the  following  circumstances.  1.  By  the 
freezing  of  the  water  in  winter,  if  the  pipe  has  not  been  laid  suffi- 
ciently deep.  2.  By  the  deposition  of  sand  and  mud  in  the 
lower  parts  of  the  pipe.  To  obviate  this,  the  water  should 
pass  through  a  strainer  before  it  enters  the  pipe.  And  if  plugs 
are  placed  at  the  lower  parts  of  the  bendings,  then  whenever 
these  are  opened,  the  water  rushes  out  with  sufficient  rapidity 
and  carries  the  deposition  with  it.  3.  By  the  penetration  of 
roots,  or  the  growth  of  aquatic  vegetables  in  the  cavity  of  the 
pipe.  This  principally  happens  in  wooden  pipes,  after  they 
begin  to  decay.  4.  By  the  collection  of  air  in  the  upper  parts 
of  the  bendings.  This  is  a  serious  evil  and  may  take  place 
in  all  pipes  which  have  an  undulating  course,  or  more  vertical 
curvatures  than  one.  When  air  is  thus  confined  in  the  pipes, 
the  water  will  not  rise  to  the  same  height  at  the  discharging  end, 

*  See  Edinbui-gh  Encyclopedia,  Art.  Hydrodynamics,  p.  494,  495. 


ARTS  OF  CONVEYING  WATER. 


307 


as  at  the  fountain  head.  The  air  being  the  lighter  fluid,  tends 
to  occupy  the  highest  part  of  the  bendings.  Any  pressure 
applied  at  the  fountain  head  tends  to  push  this  air  a  little  be- 
yond the  highest  part,  so  as  to  make  it  occupy  a  portion  of  the 
descending  side  of  the  curve.  Of  course  the  sum  of  the 
weights  in  the  descending  sides,  will  be  less  than  the  sum  of  the 
weights  in  the  ascending  sides,  and  the  fluids  will  not  be  in 
equilibrium,  except  when  the  water  at  the  fountain  head  is 
higher  than  that  at  the  discharging  end.  The  conditions  upon 
which  this  equilibrium  is  produced  are  the  same  as  those  which 
sustain  the  fluid  at  different  levels  in  Hero's  fountain,  the  spiral 
pump,  and  the  hydrostatic  lamp. 

The  prevention  of  this  evil  consists  in  avoiding  vertical 
curves,  and  in  laying  the  pipe,  if  possible,  with  an  uninterrupt- 
ed slope,  or  at  least  with  only  one  slope  in  each  direction. 
When  this  is  done,  the  air  will  escape,  at  one,  or  both,  ends  of 
the  pipe.  But  when  vertical  curves  are  unavoidable,  an  open 
tube,  the  height  of  which  is  equal  to  that  of  the  fountain  head, 
should  be  attached  to  the  highest  part  of  the  curve.  By  this 
arrangment  the  air  will  readily  escape.  In  like  manner  if  a 
tight  air  box  be  fastened  upon  the  upper  part  of  the  curve,  and 
filled  with  water,  the  air  will  escape  into  this  box  and  displace 
the  water,  without  interrupting  the  current  in  the  pipe;  The 
air  box  may  be  made  to  regulate  itself,  and  to  discharge  the 
air  when  it  is  full,  by  means  of  a  valve  in  the  top  connected 
with  a  floating,  hollow  copper  ball.  As  the  air  increases,  the 
copper  ball  will  subside  with  the  water,  till  it  opens  the  valve 
for  the  air  to  escape.  In  Fig.  1,  A  B  represents  an  undulating 
D    Fig.  1.        C  A 


308  ARTS  OF  CONVEYING  WATER. 

pipe,  of  which  A  is  the  fountain  head  and  B  the  discharging 
end.  The  water  and  air  will  arrange  themselves  as  represent- 
ed by  the  darker  and  lighter  parts  of  the  tube,  and  being  in 
equilibrium,  no  water  will  be  discharged.  If  an  upright  tube, 
C,  be  attached  to  either  of  the  upper  flexures,  it  will  discharge 
the  air  from  that  flexure.  Or  if  a  tight  box,  or  vessel,  D,  be 
substituted,  with  a  copper  float  and  valve,  it  will  have  a  similar 
effect.  Simple  punctures  made  in  the  upper  part  of  the  pipe 
also  answer  a  temporary  purpose. 

Syphon. — The  syphon  may  be  regarded  as  an  instrument 
for  the  lateral  conveyance,  rather  than  the  raising  of  water, 
since  the  fluid  must  always  be  dehvered  at  a  lower  level,  than 
that  at  which  it  is  received.  The  syphon  is  a  bent  tube,  of 
which  one  extremity,  or  leg,  is  longer  than  the  other.  If  the 
shorter  leg  be  inserted  in  a  fluid,  and  the  air  be  exhausted 
from  the  longer  leg,  by  suction  or  otherwise,  till  the  syphon  is 
full  of  water,  then  the  column  of  fluid  in  the  longer  leg  will 
preponderate,  and  a  current  will  take  place.  This  will  con- 
tinue either  till  the  water  in  the  feeding  vessel  sinks  below  the 
end  of  the  syphon,  or  that  in  the  receiving  vessel  rises  to  the 
same  height  with  the  other.  As  the  movement  depends  upon 
the  pressure  of  the  atmosphere,  water  cannot  be  raised  in  a 
syphon  to  a  greater  height  than  34  feet. 

For  practical  use  the  longer  leg  of  the  syphon  is  often  clos- 
ed with  a  stop  cock,  and  the  air  exhausted  from  it  by  a  small 
pump,  till  the  leg  is  full.  The  stop  cock  is  then  opened,  and 
the  fluid  immediately  flows  through  the  syphon. 

OF  RAISING  WATER. 

The  lateral  conveyance  of  water  is  effected  in  the  modes 
already  described,  by  the  aid  of  its  own  gravity.  The  raising 
of  water  is  effected  against  gravity,  by  the  employment  of  some 
moving  force.  Hydraulic  machines  for  raising  water,  may  be 
impelled  by  a  current,  or  fall,  of  the  water  itself,  or  by  any 
other  moving  agent.    Among  a  great  variety  of  machines  which 


ARTS  OF  CONVEYING  WATER. 


309 


have  been  constructed  for  this  use,  the  following  are  some  of 
the  most  noticeable. 

Scoop  Wheel, — If  a  water  wheel  is  provided  with  a  hollow 
axle,  and  if  in  the  place  of  spokes,  or  radii,  it  is  furnished  with 
crooked  tubes,  or  cavities,  of  a  suitable  curvature,  it  will  raise 
water  to  the  height  of  its  own  axis,  whenever  it  revolves  in  the 
direction  of  the  mouths  of  the  tubes.  Each  spoke,  or  curved 
tube,  as  it  dips  its  extremity  in  the  water,  lifts  a  certain  portion 
of  the  fluid,  and  as  the  revolution  continues,  this  water  will 
flow  through  the  tube  approaching 
nearer  to  the  axis,  until  it  is  dis- 
charged into  the  central  hollow.  To 
prevent  the  water  from  regurgitating, 
the  inner  ends  of  the  tubes  must  be 
guarded  by  valves,  or  else  made  to 
project  for  a  short  distance  into  the 
central  cavity,  as  seen  at  A  in  Fig.  2. 
In  the  latter  case  it  is  necessary  that 
they  should  enter  at  different  dis- 
tances from  the  end  of  the  axle, 
vided  into  as  many  longitudinal  compartments,  as  there  are 
tubes  in  the  wheel.  This  was  done  in  the  ancient  tympanum, 
a  machine  described  by  Vitruvius,  which  was  somewhat  similar 
in  its  principle  to  the  scoop  wheel. 

Persian  Wheel. — The  Persian  wheel,  in  certain  respects, 
resembles  the  scoop  wheel,  and  is  sometimes  combined  with  it 
in  the  same  machine.  It  differs  from  it  in  its  effect,  by  raising 
the  water  through  the  whole  diameter  of  the  wheel.  Its  form 
is  easily  understood,  by  supposing  a  number  of  buckets  to  be 
hung  round  the  circumference  of  a  water  wheel,  upon  pivots, 
at  equal  distances.  As  the  wheel  turns,  the  buckets  are  suc- 
cessively immersed  in  the  water  at  the  bottom,  and  filled. 
They  then  pass  upwards  till  they  arrive  at  the  top  of  the  wheel, 
where  they  strike  a  fixed  obstacle  and  are  overset,  discharging 
their  water  into  a  trough  placed  at  the  top  to  receive  it.  This 
machine  is  said  to  be  in  common  use  in  several  of  the  Oriental 
countries. 


Fig.  2. 


The  axle  may  also  be  di- 


310 


ARTS  OF  CONVEYING  WATER. 


JVoria.' — The  machine  used  in  Spain  under  the  name  of 
noria,  consists  of  revolving  buckets  like  the  Persian  wheel. 
But  instead  of  a  single  wheel,  two  drums,  or  trundles,  are  era- 
ployed,  and  the  buckets  are  attached  to  ropes  or  chains  passing 
round  them.  In  Spain,  earthen  pitchers  are  said  to  be  used, 
but  in  other  countries  wooden  buckets  are  employed,  like  those 
of  an  overshot  wheel.  A  sufficient  idea  of  the  form  of  the 
noria  may  be  obtained  by  inspecting  the  figure  of  the  chain 
wheel  on  page  260,  and  supposing  the  motion  reversed. 

Rope  Pump. — Instead  of  a  series  of  buckets  connected  by 
ropes  or  chains,  a  similar  effect  is  sometimes  produced  by  a 
simple  rope,  or  a  bundle  of  ropes,  passing  over  a  wheel  above, 
and  a  pulley  below,  moving  with  a  velocity  of  about  8  or  10 
feet  in  a  second,  and  drawing  up  a  certain  quantity  of  water  by 
its  friction.  It  is  probable  that  the  water  commonly  ascends  with 
about  half  the  velocity  of  the  rope.  While  the  water  is  prin- 
cipally supported  by  the  friction  of  the  rope,  its  own  cohesion 
is  sufficient  to  prevent  it  from  wholly  falling,  or  being  scattered, 
by  any  accidental  inequality  of  the  motion.  The  portion  raised 
is  collected  in  a  trough  at  the  top. 

Hydreole. — This  name  is  given  by  M.  Mannoury  Dectot,  to 
an  invention  for  raising  water  by  the  admixture  of  atmospheric 
air.  If  a  column  of  water  be  intimately  mixed  with  air  in 
small  bubbles,  the  air  will  occupy  some  time  in  ascending  to 
the  surface,  and  the  mean  while  the  collective  specific  gravity 
of  the  whole  column  will  be  much  less,  than  if  it  consisted  of 
water  alone.  If  a  vertical  tube  be  placed  in  a  reservoir  of 
water,  and  if  a  quantity  of  air  be  injected  into  the  bottom  of 
the  tube,  by  a  bellows,  or  forcing  pump,  the  water  in  the  tube 
will  immediately  rise  to  a  higher  level,  and  remain  until  the  air 
has  escaped  at  the  top.  And  if  the  tube  be  of  proper  height, 
the  water  will  overflow  in  the  same  manner  as  it  does  during  the 
ebullition  of  boiling  liquids.  This  appears,  however,  not  to  be 
a  very  economical  mode  of  applying  force. 

Archimedes^  Screiv. — This  name  is  given  to  a  machine  form- 
ed by  one  or  more  pipes  wound  spirally  round  a  cylinder  which 


ARTS  OF  CONVEYING  WATER. 


311 


revolves  on  an  axis  in  an  oblique  situation.  It  is  used  in  some 
places  under  the  name  of  water  snail.  Its  mode  of  operation, 
may  be  easily  conceived,  by  supposing  a  tube,  formed  into  a 
hoop,  to  be  rolled  up  an  inclined  plane,  in  which  case  the  fluid 
would  be  forced,  by  the  elevation  of  the  tube  behind  it,  to  rua 
as  it  were  up  hill.  The  screw  is 
usually  turned  by  a  water  wheel.  Dur- 
ing each  revolution  the  lower  end  of 
each  spiral  tube  is  immersed  in  the 
water  and  dips  up  a  certain  quantity. 
This  water,  by  its  gravity,  keeps  to 
the  lower  side  of  the  screw,  as  seen 
in  Fig.  3,  but  at  the  same  time,  in 
consequence  of  the  revolutions  of 
the  screw,  it  passes  continually  upward  until  it  is  delivered  at 
the  highest  end. 

This  instrument  is  sometimes  made  by  fixing  a  spiral  parti- 
tion round  a  cylinder,  and  covering  it  with  an  external  coating, 
either  of  wood  or  of  metal.  It  should  be  so  placed  with  re- 
spect to  the  surface  of  the  water,  as  to  fill  in  each  turn  one 
half  of  a  convolution  ;  for  when  the  orifice  remains  always  im- 
mersed, its  efiect  is  much  diminished.  It  is  generally  inclined 
to  the  horizon  in  an  angle  of  between  45  and  60  degrees ; 
hence  it  is  obvious  that  its  utility  is  limited  to  those  cases  in 
which  the  water  is  only  to  be  raised  to  a  moderate  height. 
The  spiral  is  seldom  single,  but  usually  consists  of  three  or 
four  separate  coils,  forming  a  screw  which  rises  more  rapidly 
round  the  cylinder. 

A  water  screw  which  operates  in  a  similar  manner,  may  be 
made  by  a  spiral  partition  wound  upon  a  central  axis,  and  re- 
volving by  itself  within  a  smooth  hollow  cylinder,  to  the  cavity 
of  which  it  is  nearly  fitted.  In  this  form,  however,  there  is 
some  loss  by  the  leakage  between  the  screw  and  the  cylinder 
which  contains  it. 

Spiral  Pump. — This  machine  is  formed  by  a  spiral  pipe 
consisting  of  many  convolutions,  arranged  either  in  a  single 


312 


ARTS  OF  CONVEYING  WATER. 


plane,  as  in  Fig.  4,  or  in  a  cylindrical  or  Fi'g-  4, 

conical  surface,  and  revolving  round  a 
horizontal  axis.  The  pipe  is  connected 
at  one  end,  by  a  central  water  tight 
joint,  to  an  ascending  pipe,  while  the  oth- 
er end  receives,  during  each  revolution, 
nearly  equal  quantities  of  air  and  water.  It 
was  invented  about  1 746,  by  Andrew  Wirtz, 
a  pewterer  at  Zurich,  whence  it  is  often  called  the  Zurich  ma- 
chine. It  is  said  to  have  been  used  with  great  success  at  Flo- 
rence, and  in  Russia.  Dr  Young  states  that  he  has  made  use 
of  it  for  raising  water  to  a  height  of  forty  feet.  The  end  of 
the  pipe  is  furnished  with  a  spoon,  containing  as  much  water  as 
will  fill  half  of  one  of  its  coils.  The  water  enters  the  pipe  a 
little  before  the  spoon  has  arrived  at  its  highest  situation,  the 
other  half  remaining  full  of  air.  The  air  communicates  the 
pressure  of  the  column  of  water  to  the  preceding  portion,  and 
in  this  manner  the  effect  of  nearly  all  the  water  in  the  wheel  is 
united,  and  becomes  capable  of  supporting  the  column  of  water, 
or  of  water  mixed  with  air,  in  the  ascending  pipe.  The  air 
nearest  the  joint  is  compressed  into  a  space  much  smaller  than 
that  which  it  occupied  at  its  entrance,  so  that  where  the  height 
is  considerable,  it  becomes  advisable  to  admit  a  larger  portion 
of  air  than  would  naturally  fill  half  the  coil.  This  lessens  the 
quantity  of  water  raised,  but  it  lessens  also  the  force  required  to 
turn  the  machine.  The  joint  should  be  conical,  in  order  that 
it  may  be  tightened  when  it  becomes  loose,  and  the  pressure 
ought  to  be  removed  from  it  as  much  as  possible.  The  loss  of 
power,  supposing  the  machine  well  constructed,  arises  only 
from  the  friction  of  the  water  on  the  pipes,  and  the  friction  of 
the  wheel  on  its  axis;  and  where  a  large  quantity  of  water' is 
to  be  raised  to  a  moderate  height,  both  of  these  resistances  may 
be  rendered  inconsiderable.  But  when  the  height  is  very  great, 
the  length  of  the  spiral  must  be  much  increased,  so  that  the 
weight  of  the  pipe  becomes  extremely  cumbersome,  and  causes 
a  great  friction  on  the  axis,  as  well  as  a  strain  on  the  machinery. 


ARTS  OF  CONVEYING  WATER. 


313 


Centrifugal  Pump. — The  centrifugal  force,  has  sometimes 
been  employed,  in  conjunction  with  the  pressure  of  the  atmos- 
phere, as  an  immediate  agent  in  raising  water,  by  means  of  a 
rotary  pump.  The  machine  called  a  centrifugal  pump,  con- 
sists of  a  vertical  pipe,  capable  of  revolving  round  its  axis,  and 
connected  above  with  a  horizontal  pipe,  which  is  open  at  one, 
or  at  both  ends,  the  whole  being  furnished  with  proper  valves 
to  prevent  the  escape  of  the  water,  when  the  machine  is  at 
rest.  As  soon  as  the  rotation  becomes  sufficiently  rapid,  the 
centrifugal  force  of  the  water  in  the  horizontal  pipe  causes  it 
to  be  discharged  at  the  ends,  its  place  being  supplied  by  means 
of  the  pressure  of  the  atmosphere  on  the  reservoir  below, 
which  forces  the  water  to  ascend  through  the  vertical  pipe.  This 
machine  may  be  so  arranged,  that,  according  to  theory,  very  lit- 
tle of  the  force  applied  is  lost ;  but  it  Fig.  5. 
has  failed  of  producing  in  practice  a 
very  advantageous  effect.  In  Fig.  5, 
a  centrifugal  pump  is  represented. 
The  machine  is  first  filled  with  water 
through  the  funnel  A,  while  the  valve 
at  D  prevents  the  water  from  descend- 
ing. The  whole  is  then  made  to  turn 
rapidly,  and  the  water  is  discharged 
from  the  ends  of  the  horizontal  part, 
into  a  circular  trough,  a  section  of 
which  is  seen  at  B  and  C. 

Common  Pumps. — A  pump  is  a  machine  so  well  known, 
and  so  generally  used,  that  the  denomination  has  sometimes 
been  extended  to  hydraulic  machines  of  all  kinds.  The  term, 
however,  in  its  strictest  sense,  is  to  be  understood  of  those  ma- 
chines, in  which  the  water  is  raised  by  the  motion  of  one  solid 
within  another,  and  this  motion  is  usually  alternate,  but  some- 
times continued,  so  as  to  constitute  a  rotation.  In  the  pumps 
most  commonly  used,  a  cavity  is  enlarged  and  contracted  by 
turns,  the  water  being  admitted  into  it  through  one  valve,  and 
discharged  through  another. 
40 


ARTS  OF  CONVEYING  WATER. 

The  coinmon  household  pump  has  otherwise  been  called  the 
sucking  pump,  from  the  circumstance  that  the  water  is  raised 
m  it,  by  the  pressure  of  the  atmosphere.  In  this  country, 
pumps  are  made  for  common  use,  both  in  wells,  and  in  ships, 
by  boring  logs  so  as  to  produce  a  large  hollow,  and  inserting 
two  hollow  wooden  plugs  called  boxes,  at  different  heights,  both 
of  which  are  furnished  with  valves,  or  clappers,  opening  up- 
wards. The  lower  box  is  made  stationary,  and  Fig.  6. 
serves  merely  to  prevent  the  water  which  is  rais- 
ed, from  running  back.  The  upper  box  is  a  hol- 
low moveable  piston,  attached  by  its  rod  to  the 
handle  or  brake,  of  the  pump.  When  the  pump 
is  full  of  water,  every  stroke  of  the  handle  raises 
this  box,  together  with  the  column  of  water  above 
it.  When  the  handle  is  lifted,  the  box  is  pushed 
further  down  into  the  water,  while  its  valve  opens 
to  allow  the  water  to  pass  through.  In  Fig.  6, 
this  pump  is  represented  with  the  box  just  begin- 
ning to  descend.  The  valve  then  shuts,  and  the 
second  stroke  of  the  pump  raises  another  column 
of  water  to  the  spout.  As  the  action  of  this  pump  depends 
upon  the  pressure  of  the  atmosphere,  water  cannot  be  raised 
by  it  from  a  depth  of  more  than  34  feet  below  the  upper  valve, 
and  in  practice  a  much  shorter  limit  is  commonly  assigned. 

Forcing  Pump. — The  forcing  pump  differs  Fig.  l.b 
from  the  common  sucking  pump  just  described, 
in  having  a  solid  piston  without  a  valve,  and  the 
spout,  or  discharging  orifice,  placed  below  the 
piston.  When  the  piston  is  raised,  the  lower 
valve  of  the  pump  rises  and  admits  the  water 
from  below,  as  in  the  common  pump.  But 
when  the  piston  is  depressed,  the  water  is  thrown 
out  through  a  spout  in  the  side,  which  has  a 
valve  opening  outward,  at  a,  in  Fig  7.  In  a 
forcing  pump  the  water  cannot  be  brought  from 
a  depth  of  more  than  34  feet  below  the  piston, 
but  it  can  afterwards  be  sent  up  to  any  height 


Sl4 


ARTS  OF  CONVEYING  WATER. 


315 


desired,  in  a  pipe  a  b,  because  the  pressure  communicated  by 
the  downward  stroke  of  the  piston,  is  not  dependent  on  the 
pressure  of  the  atmosphere,  but  upon  the  direct  force  applied 
to  the  piston. 

Plunger  Pump.— A  very  effectual  pump  for  raising  a 
large  quantity  of  water  to  a  small  height,  is  shown  in  Fig.  8. 

Fig.  8. 


D 


It  is  made  by  fitting  two  upright  beams  or  plungers,  A  and  B, 
of  equal  thickness  throughout,  into  cavities  nearly  of  the  same 
size,  allowing  them  only  room  to  move  without  friction,  and 
connecting  the  plungers  together  by  a  horizontal  beam  moving 
on  a  pivot.  The  water  being  admitted,  during  the  ascent  of 
each  plunger,  by  a  large  valve  in  the  bottom  of  the  cavity,  at 
C  and  D  ;  it  is  forced,  when  the  plunger  descends,  to  escape 
through  a  second  valve  at  E  or  F,  in  the  side  of  the  cavity, 
and  to  ascend  by  a  wide  pipe  to  the  top  of  the  machine.  The 
plungers  ought  not  to  be  in  any  degree  tapered,  because  in  this 
case  a  great  force  would  be  unnecessarily  consumed,  when 
they  descend,  in  throwing  out  the  water,  with  great  velo- 
city, from  the  interstice  formed  by  their  elevation.  This 
pump  may  be  worked  by  a  laborer  walking  backwards  and 
forwards,  either  on  the  beam,  or  on  a  board  suspended  below 
it.  By  means  of  an  apparatus  of  this  kind,  described  by 
Professor  Robison,  an  active  man,  loaded  with  a  weight  of  30 
pounds,  has  been  able  to  raise  580  pounds  of  water  every 
minute,  to  a  height  of  llj  feet,  for  ten  hours  a  day,  without 


316 


ARTS  OF  CONVEYING  WATER. 


fatigue.  This,  says  Dr  Young,  is  the  greatest  effect  produced 
by  a  laborer  that  has  ever  been  correctly  stated  by  any  author; 
It  is  equivalent  to  somewhat  more  than  1 1  pounds  raised  through 
10  feet  in  a  second,  instead  of  10  pounds,  which  is  a  fair  esti- 
mate of  the  usual  force  of  a  man,  without  any  deduction  for 
friction. 

Delahire^s  Pump. — A  pump,  partaking  of  the  nature  of  a 
forcing  and  a  sucking  pump,  is  sometimes  called  a  mo^ec^  pump. 
In  Delahire's  pump,  which  is  of  this  kind,  and       Fig.  9. 
shown  in  Fig.  9,  the  same  piston  is  made  to 
serve  a  double  purpose,  the  rod  working  in  a 
collar  of  leathers,  and  the  water  being  admitted 
and  expelled  in  a  similar  manner,  above  and 
below  the  piston,  by  means  of  a  double  appar- 
atus of  valves  and  pipes.    When  the  piston  is 
depressed,  the  water  enters  the  barrel  at  the 
valve  A,  and  goes  out  at  B.     When  the 
piston  is  elevated,  it  enters  at  C,  and  escapes 
at  D. 

For  forcing  pumps  of  all  kinds,  the  common  piston,  with  a 
collar  of  loose  and  elastic  leather,  is  preferable  to  those  of  a 
more  complicated  structure.  The  pressure  of  the  water  on  the 
inside  of  the  leather  makes  it  sufficiently  tight,  and  the  friction 
is  inconsiderable.  In  some  pumps  the  leather  is  omitted,  for 
the  sake  of  simplicity,  the  loss  of  water  being  compensated  by 
the  greater  durability  of  the  pumps  ;  and  this  loss  will  be  the 
smaller  in  proportion  as  the  motion  of  the  piston  is  more  rapid. 

Hydrostatic  Press. — This  powerful  machine  is  essentially  a 
forcing  pump,  aided  in  its  action  by  the  well  known  properties 
of  hydrostatic  pressure.  It  appears  to  have  been  invented  by 
Pascal,  previously  to  1664,  and  recommended  by  him  as  a  new 
mechanical  power.  It  was,  however,  practically  lost  sight  of, 
till  it  was  reinvented  by  Mr  Bramah,  more  than  a  century  af- 
terwards. In  this  press  the  water  is  forced,  by  a  small  pump, 
into  a  strong  iron  cylinder,  in  which  it  acts  on  a  much  larger 
piston ;  consequently  this  piston  is  urged  by  a  force  as  much 


ARTS  OF  CONVEYING  WATER. 


greater  than  that  which  acts  on  the  first 
pump  rod,  as  its  surface  is  greater  than 
that  of  the  small  one.  In  Fig.  10,  the 
water  is  forced  by  the  pump  A  through 
the  pipe  B,  into  the  cylinder  C,  in 
which  it  acts  very  powerfully  upon  the 
large  piston  D,  and  raises  the  bottom 
of  the  press  E.  The  upward  force, 
by  which  the  material  above  E  is  com- 
pressed, exceeds  the  force  which  is  applied  to  the  pump,  as 
much  as  the  surface  of  the  piston  D,  exceeds  that  of  the  piston 
of  the  pump.  Tn  practice,  the  cylinder  C  requires  to  be  made 
much  thicker  than  here  represented. 

Lifting  Pump. — Where  the  height  through  which  the  water 
is  to  be  raised  is  considerable,  some  inconvenience  might  arise 
from  the  length  of  the  barrel  through  which  the  piston  rod  of  a 
sucking  pump  would  have  to  descend,  in  order  that  the  piston 
might  remain  within  the  limits  of  atmospheric  pressure.  This 
may  be  avoided  by  placing  the  moveable  valve  below  the  fixed 
valve,  and  introducing  the  piston  at  the  bottom  of  the  bar- 
rel. It  is  then  worked  by  means  of  a  frame  on  the  outside. 
Such  a  machine  is  called  a  lifting  pump.  In  common  with 
other  forcing  pumps,  it  has  the  disadvantage  of  thrusting  the 
piston  before  the  rod,  and  thus  tending  to  bend  the  rod,  and 
produce  an  unequal  friction  on  the  piston,  while,  in  the  sucking 
pump,  the  principal  force  always  tends  to  straighten  the  rod. 

Bag  Pump. — A  bag  of  leather  has  sometimes  Fig.  11. 
been  employed  for  connecting  the  piston  of  a 
pump  with  the  barrel,  and  in  this  manner  nearly  all 
friction  is  avoided.  It  is  probable,  however,  that 
the  want  of  durability  would  be  a  great  objection  to 
such  a  machine.  In  Fig.  11,  A  represents  a 
leathern  bag  attached  to  a  number  of  hoops. 
This  bag  is  ahernately  extended  and  contracted, 
like  a  bellows,  by  every  stroke  of  the  piston,  and 
raises  the  water  without  friction  against  the 
pump. 


318 


ARTS  OF  CONVEYING  WATER. 


Double  acting  Pump. — The  rod  of  a  sucking  pump  may 
also  be  made  to  work  in  a  collar  of  leather  at  the  top,  as  at  A 
in  Fig.  12,  and  the  water  may  be  forced  through  Fig.  12.  B 
a  valve  into  an  ascending  pipe  B.  By  applying 
an  air  vessel  to  this,  or  to  any  other  forcing  pump, 
as  is  done  in  fire  engines,  its  motion  may  be  equal- 
ized, and  its  performance  improved  ;  for  if  the  ori- 
fice be  large  enough,  the  water  may  be  forced  into 
the  air  vessel,  during  the  stroke  of  the  pump,  with 
any  velocity  that  may  be  required,  and  with  little 
resistance  from  friction  ;  whereas  the  loss  of  force, 
from  the  frequent  accelerations  and  retardations  of 
the  whole  body  of  water,  in  a  long  pipe,  must  always  be  consider- 
able. The  condensed  air,  reacting  on  the  water,  expels  it 
more  gradually,  and  in  a  continual  stream,  so  that  the  air  ves- 
sel has  an  effect  analogous  to  that  of  a  fly  wheel  in  mechanics. 

Rolling  Pump. — A  pump  of  this  Fig-  13. 

kind  is  formed  by  a  barrel,  or  hollow  ^^J^^^^^^'^^^^^jv 
cylinder,  shown  in  section  in  Fig.  13, 

having  two  partitions.    One  of  these,   ?  ^       ^  % 

AB  is  fixed,  and  the  other  C  D,  is  d  ^  -^^E^  * 

composed  of  two  wings,  or  valves, 
capable  of  an  alternate  motion  about  — -^^^^ 
the  axis  of  the  cylinder.  When  the  partition  C  D  turns  in  one 
direction,  the  water  in  the  cavity  C  is  driven  out  at  the  ori- 
fice a,  and  will  rise  in  a  pipe  attached  to  that  orifice.  At  the 
same  time  the  water  in  the  cavity  D  is  forced  out  at  the  ori- 
fice d.  While  this  is  taking  place,  fresh  portions  of  water  en- 
ter the  remaining  cavities  at  w  and  z.  When  the  partition  CD 
has  moved  as  far  as  possible,  it  then  returns  in  the  opposite  di- 
rection and  drives  out  the  water  through  xj  and  a?,  and  receives 
fresh  water  through  h  and  c.  The  orifices  which  receive  the 
water  have  valves  opening  inward,  and  those  which  discharge 
it  have  valves  •  opening  outward.  The  machine  is  worked  by 
arms  attached  to  the  axis  of  the  cylinder,  which  for  this  pur- 
pose projects  through  a  collar  in  the  ends  of  the  vessel. 


ARTS  OF  CONVEVING  WATER. 


319 


For  the  sake  of  simplicity,  a  sector  of  a  cylinder,  is  some- 
times used,  in  which  case  a  single  partition,  or  valve,  like  a  door 
on  hinges,  traverses  the  whole  cavity,  and  only  half  the  number 
of  orifices  are  necessary,  to  admit  and  discharge  the  water. 
Fire  engines,  for  projecting  water,  have  been  constructed  in 
both  these  methods  by  different  inventors. 

Eccentric  Pump. — The  eccentric  pump,  ^^S- 
a  section  of  which  is  shown  at  Fig.  14, 
consists  of  a  hollow  cylinder  a  d,  in  the  in- 
terior of  which  a  solid  cylinder  b,  of  the 
same  length,  but  of  about  half  the  diameter, 
is  made  to  revolve,  by  its  axle  passing  through 
water  tight  collars  in  the  ends  of  the  exterior 
cylinder.  The  internal  cylinder  is  so  plac- 
ed, that  its  surface  comes  in  contact  with 
some  part  of  the  internal  surface  of  the 
larger  cylinder.  The  surface  of  the  small 
cylinder,  is  also  furnished  with  four  large  valves,  or  flaps, 
turning  on  hinges,  and  partaking  of  its  own  curvature,  so  that 
when  they  are  shut  down,  they  form  no  projections,  but  appear 
as  parts  of  the  same  cyhnder.  These  valves  are  made  to 
open  by  springs  or  otherwise,  so  that  when  one  of  them  is 
brought  by  the  revolution  of  the  internal  cylinder  into  the  nar- 
rowest part  of  the  internal  space,  it  is  pressed  down  and  shut ; 
but  as  the  inner  cylinder  moves  on,  the  valve  being  gradually 
carried  forward,  will  continue  to  open  until  it  arrives  at  the 
widest  part  of  the  cavity.  It  is  then  pressed  down  again  by  a 
continuation  of  the  revolution.  In  this  way  the  water  behind 
the  valve  is  drawn  up  from  the  feeding  pipe  by  the  atmospheric 
pressure,  while  that  before  the  valve  is  forced  upward  into  the 
delivering  pipe.  As  each  of  the  valves  performs  the  same 
operation  in  its  turn,  this  pump  affords  a  constant  supply  of 
water. 

Rotative  steam  engines  have  been  constructed  by  different 
projectors,  on  the  principle  of  this  pump,  as  well  as  the 
following. 


320 


ARTS  OF  CONVEYING  WATER. 


Another  form  of  an  eccentric  pump,  is  seen  Fig-  1^. 
in  Fig.  15.  The  roller,  or  solid  cylinder.  A, 
revolving  within  the  reservoir,  or  hollow  cy- 
linder, B  F,  carries  with  it  the  slider,  D  E, 
which  is  made  to  sweep  the  internal  surface 
of  this  cylinder  by  revolving  in  the  direction 
from  C  to  F,  so  that  the  water  is  drawn  up 
by  the  pipe  C,  and  discharged  by  the  pipe  F. 

An  objection  to  all  pumps  of  this  sort,  is,  that  if  they  are 
made  tight  enough  to  hold  water,  they  occasion  a  great  degree 
of  friction  on  account  of  the  extensive  contact  of  the  moving 
surfaces.  The  continual  change,  also,  which  takes  place,  both 
in  the  direction  and  velocity  of  the  water,  is  productive  of 
great  resistance  from  inertia.  The  stream  at  the  deHvering 
orifice,  although  never  wholly  intermitted,  is  by  no  means  uni- 
form in  its  velocity. 

Arrangement  of  Pipes. — The  pipes,  through  which  wa- 
ter is  raised,  by  pumps  of  any  kind,  ought  to  be  as  short 
and  as  straight  as  possible.  Thus,  if  we  have  to  raise  water  to 
a  height  of  20  feet,  and  to  carry  it  to  a  horizontal  distance  of 
100,  by  means  of  a  forcing  pump,  it  will  be  more  advanta- 
geous to  raise  it  first  vertically  into  a  cistern  20  feet  above  the 
reservoir,  and  then  to  let  it  run  along  horizontally,  or  find  its 
level  in  a  bent  pipe,  than  to  connect  the  pump  immediately 
with  a  single  pipe,  carried  to  the  place  of  its  destination.  And 
for  the  same  reason  a  sucking  pump  should  be  placed  as  nearly 
over  the  well  as  possible,  in  order  to  avoid  a  loss  of  force  in 
working  it.  If  very  small  pipes  are  used,  they  will  much  in- 
crease the  resistance,  by  the  friction  which  they  occasion. 

Chain  Pump. — Water  has  sometimes  been  raised  by  stuffed 
cushions,  or  by  oval  blocks  of  wood,  connected  with  an  endless 
rope,  or  chain,  and  caused,  by  means  of  two  wheels,  or  drums, 
to  rise  in  succession  in  the  same  barrel,  carrying  the  water  in  a 
continual  stream  before  them.  The  magnitude,  however,  of 
the  friction,  appears  to  be  an  objection  to  this  method.  From 
the  resemblance  of  the  apparatus  to  a  string  of  beads,  it  has 


ARTS  OF  CONVEYING  WATER. 


321 


been  called  a  head  pump,  or  paternoster  work.  When  flat 
boards  are  united  by  chains,  and  employed  instead  of  these 
cushions,  the  machine  has  been  denominated  a  cellular  pump  ; 
and  in  this  case  the  barrel  is  usually  square,  and  placed  in  an 
inclined  position.  There  is,  however  a  considerable  loss  from 
the  facility  with  which  the  water  runs  back.  The  chain 
pump,  used  in  the  navy,  is  a  pump  of  this  kind,  with  an  upright 
barrel,  through  which  leathers,  strung  on  a  chain,  are  drawn  in 
constant  succession.  These  pumps  are  only  employed  when  a 
large  quantity  of  water  is  to  be  raised,  and  they  must  be  work- 
ed with  considerable  velocity  in  order  to  produce  any  effect  at  all. 

The  Chinese  work  their  cellular  pumps,  or  bead  pumps,  by 
walking  on  bars  which  project  from  the  axis  of  the  wheel,  or 
drum  that  drives  them,  and  whatever  objection  may  be  made 
to  the  choice  of  the  machine,  the  mode  of  communicating  mo- 
tion to  it  must  be  allowed  to  be  advantageous. 

Schemnitz  T^essels,  or  Hungarian  Machine, — The  mediation 
of  a  portion  of  air,  is  employed  for  raising  water,  not  only  in 
the  spiral  pump,  but  also  in  the  air  vessels  of  Schemnitz,  in  the 
manner  shown  in  Fig.  16.  A  column  of  water,  Fig,  ig, 
descending  through  a  pipe  C,  into  a  closed  re- 
servoir, B,  containing  air,  obliges  the  air  to  act, 
by  means  of  a  pipe  D,  leading  from  the  upper 
part  of  the  reservoir  or  air  vessel,  on  the  water 
in  a  second  reservoir.  A,  at  any  distance  either 
below  or  above  it,  and  forces  this  water  to  as- 
cend through  a  third  pipe,  E,  to  any  height 
less  than  that  of  the  first  column.  The  air 
vessel  is  then  emptied,  the  second  reservoir 
filled,  and  the  whole  operation  repeated.  The 
air  mtist,  however,  acquire  a  density,  equivalent 
to  the  pressure,  before  it  can  begin  to  act ;  so 
that  if  the  height  of  the  columns  were  34  feet,  it  must  be  re- 
duced to  half  its  dimensions  before  any  water  would  be  raised  ; 
and  thus  half  of  the  force  would  be  lost.  But  where  the 
height  is  small,  the  force  lost  in  this  manner  is  not  greater  than 
41 


322 


AKTS  OP  CONVEYING  WATER. 


that  which  is  usually  spent  in  overcoming  friction,  and  other 
imperfections  of  the  machinery  employed  ;  for  the  quantity  of 
water,  actually  raised  by  any  machine,  is  not  often  greater  than 
half  the  power  which  is  consumed.  The  force  of  the  tide,  or 
of  a  river  rising  and  falling  with  the  tide,  might  easily  be  ap- 
plied by  a  machine  of  this  kind,  to  the  purpose  of  raising  water. 
Thus  if  at  low  tide  the  vessel  A  was  filled  with  air,  then  at 
high  tide  the  water  flowing  down  the  tube  E,  would  cause  the 
water  in  the  vessel  B  to  ascend  in  the  pipe  C. 

Heroes  Fountain. — The  fountain  of  Hero,  precisely  resem- 
bles in  its  operation,  the  hydraulic  vessels  of  Schemnitz,  which 
were  probably  suggested  to  their  inventor  by  the  construction 
of  this  fountain.  It  may  be  used  simply  to  raise  water,  or  to 
project  it  upwards  in  the  form  of  a  jet,  as  in  Fig.  Fig-.  17. 
17.  The  first  reservoir  C  of  the  fountain  is 
lower  than  the  orifice  of  the  jet.  A  pipe  de- 
scends from  it  to  the  air  vessel,  B,  which  is  at 
some  distance  below,  and  the  pressure  of  the 
air  is  communicated,  by  an  ascending  tube,  D, 
to  a  third  cavity.  A,  containing  the  water  which 
supplies  the  jet.  In  this  form  of  the  machine,  the 
water  will  continue  to  spout  from  the  pipe  E, 
until  all  the  water  in  the  reservoir  C,  has  de- 
scended into  the  vessel  B.  The  principle  of 
Hero's  fountain  has  been  applied  to  raise  oil 
in  lamps,  and  one  of  its  most  simple  forms  has  already  been 
described  under  the  head  of  hydrostatic  lamp,  page  179. 

Atmospheric  Machines. — The  spontaneous  vicissitudes  of 
the  pressure  of  the  air,  occasioned  by  changes  in  the  weight 
and  temperature  of  the  atmosphere,  have  been  applied  by 
means  of  a  series  of  reservoirs,  furnished  with  proper  valves, 
to  the  purpose  of  raising  water  by  degrees  to  a  moderate  height. 
But  it  seldom  happens  that  such  changes  are  capable  of  pro- 
ducing an  elevation  in  the  water  of  each  reservoir  of  more  than 
a  few  inches,  or  at  most  a  foot  or  two,  in  a  day;  and  the  whole 
quantity  raised,  must  therefore  be  inconsiderable. 


ARTS  OF  CONVEYING  WATER. 


323 


Hydraulic  Ram. — The  momentum  of  a  stream  of  water, 
flowing  through  along  pipe,  has  also  been  employed  for  raising 
a  small  quantity  of  water  to  a  considerable  height.  The  pas- 
sage of  the  pipe  being  stopped  by  a  valve,  which  is  raised  by 
the  stream,  as  soon  as  its  motion  becomes  sufficiently  rapid, 
the  whole  column  of  fluid  must  necessarily  concentrate  its  ac- 
tion almost  instantaneously  on  the  valve.  In  this  manner 
it  loses  the  characteristic  property  of  hydraulic  pressure,  and 
acts  as  if  it  were  a  single  solid ;  so  that,  supposing  the  pipe  to 
be  perfectly  elastic,  and  inextensible,  the  impulse  may  over- 
come any  pressure  however  great,  that  might  be  opposed  to  it. 
If  the  valve  opens  into  a  pipe  leading  to  an  air  vessel,  a 
certain  quantity  of  the  water  will  be  forced  in,  so  as  to  con- 
dense the  air,  more  or  less  rapidly,  to  the  degree  that  may  be 
required  for  r^iising  a  portion  of  the  water  contained  in  it,  to  a 
given  height.  JMr  Whitehurst  appears  to  have  been  the  first 
that  employed  this  method  ;  it  was  afterwards  improved  by  Mr 
Boulton  ;  and  the  same  machine  has  attracted  much  attention 
in  France  under  the  denomination  of  the  hydraulic  ram  of  M. 
Montgolfier. 

Fig.  18  represents  this  machine.    When  the  water  in  the 


Fig.  18. 


pipe  A  B  has  acquired  sufficient  velocity,  it  raises  the  valve  B, 
which  immediately  stops  its-  further  passage.  The  momentum 
which  the  water  has  acquired  will  then  force  a  portion  of  it 
through  the  valve  C  into  the  air  vessel  D.  The  condensed 
air  at  D,  causes  the  water  to  rise  into  the  pipe  E,  as  long  as 
the  effect  of  the  horizontal  column  continues.  When  the  water 
becomes  quiescent,  the  valve  B  will  open  again  by  its  own 


324 


ARTS  OF  CONVEYING  WATER. 


weight,  and  the  current  will  be  renewed,  until  it  acquires  force 
enough  to  shut  the  valve,  and  repeat  the  operation. 

OF  PROJECTING  WATER. 

If  a  degree  of  force,  or  pressure,  be  applied  to  water  suffi- 
cient to  raise  it  through  a  tube  to  a  given  height,  the  same 
force  would  also  cause  it  to  spout  through  an  orifice,  in  a  con- 
tinued stream,  or  jet,  to  nearly  the  same  height,  in  common 
cases.  The  height,  however,  can  never  be  fully  as  great,  for 
various  reasons.  One  of  these  is  found  in  the  friction  of  the 
ajutage,  or  discharging  orifice,  which  acts  as  a  retarding  force. 
Another  obstacle  is  the  resistance  of  the  atmosphere,  which 
increases  in  a  rapid  ratio,  as  the  velocity  of  the  water  becomes 
greater,  and  which  is  also  greatly  augmented  as  the  water  di- 
vides, and  spreads  out  a  greater  surface  to  the  resistance  of 
the  air.  A  third  obstacle  consists  in  the  resistance  which  the 
water  offers  to  itself.  The  parts  first  projected,  being  constant- 
ly retarded  in  their  ascent  by  gravity  and  atmospheric  resist- 
ance, oppose  the  progress  of  the  parts  which  are  last  projected, 
and  which  have  the  greatest  velocity.  And  as  fluids  move  in 
all  directions,  this  impulse  of  different  parts  of  the  water  against 
each  other,  tends  to  widen,  and  consequently  to  shorten  the 
column.  In  a  vertical  jet,  moreover,  the  weight  of  the  falling 
water  opposes  the  ascending  column,  and  hence  a  fluid  will 
spout  higher,  if  the  jet  be  turned  a  Httle  to  one  side,  than  if  it 
be  perpendicular. 

Fountains. — Artificial  fountains  which  throw  a  perpetual  jet 
of  water,  usually  act  by  the  pressure  of  a  reservoir  of  water, 
situated  at  a  greater  height  than  that  of  the  jet  produced.  The 
water  is  conveyed  from  the  reservoir  to  the  place  of  the  foun- 
tain, in  pipes,  and  if  the  orifice  from  which  it  issues  be  directed 
upward,  it  will  spout  to  a  height  approaching  that  of  the  reser- 
voir. It  will  always,  however,  fall  short  of  this  height,  for  the 
reasons  already  stated  ;  and  the  difference  will  be  greater  in 
jets  of  great  height,  than  it  is  in  lower  ones ;  since  it  is  found 


ARTS  OF  CONVEYING  WATER. 


325 


by  experiment,  that  the  differences  between  the  heights  of  the 
jets  and  of  the  reservoirs,  are  as  the  squares  of  the  heights  of 
the  jets  themselves.  *  Fountains  are  chiefly  used  for  purposes 
of  ornament,  and  when  of  large  size  require  to  be  fed  from 
the  elevated  parts  of  rivers,  or  bodies  of  water  having  a  high 
level.  At  PeterhofF,  in  Russia,  there  are  two  fountains  which 
spout  a  column  of  water  9  inches  in  diameter,  to  the  height  of 
sixty  feet,  and  the  fall  of  the  returning  water  produces  a  concus- 
sion sufficient  to  shake  the  ground. 

Fire  Engines. — The  engines  used  for  extinguishing  fires  in 
buildings,  are  in  effect  a  species  of  forcing  pumps,  in  which 
the  water  is  subjected  to  pressure  sufficiently  strong  to  raise  it, 
by  a  jet  or  otherwise,  to  the  required  height.  But  if  the  forc- 
ing pump  were  used  alone,  the  water  would  issue  only  in  in- 
termitting jets,  in  consequence  of  the  reciprocating  motion  of 
the  pump,  and  thus  a  great  part  of  it  would  become  ineffectual. 
In  order  to  make  the  discharge  uniform,  and  thus  keep  up  a 
continual  stream,  a  strong  vessel  filled  with  air,  is  attached  to 
the  engine.  Into  this  vessel  the  water  is  forced  by  the  pumps, 
and  as  the  air  cannot  escape,  it  is  condensed  in  proportion  as 
the  water  accumulates,  until  it  reacts  upon  the  surface  of  the 
water  with  great  power.  If  the  air  be  condensed  into  half  the 
space  which  it  originally  occupied,  it  will  act  upon  the  water 
with  a  pressure  equal  to  that  of  two  atmospheres,  and  vdll  be 
adequate  to  raise  water  through  a  tube  to  the  height  of  33  feet, 
or  to  project  it  through  the  atmosphere  to  nearly  the  same 
height.  When  the  air  is  condensed  to  one  third  of  its  former 
volume,  in  consequence  of  the  air  vessel  being  two  thirds  filled 
with  water,  its  elasticity  will  be  three  times  greater  than  that  of 
the  atmosphere.  It  w^ill  therefore  raise  water  in  a  tube  to  the 
height  of  66  feet,  and  would  throw  it  to  nearly  the  same  height 
were  it  not  for  the  resistances,  which  have  already  been  ex- 
plained. 

The  foregoing  principle  of  the  fire  engine  has  been  variously 
modified,  by  adapting  different  kinds  of  pumps  to  the  air  ves- 

*  Ascertained  by  Mariotte.    Bossut,  Tom.  ii.  §  615. 


326 


ARTS  OF  CONVEYING  WATER. 


sel,  and  by  altering  various  details.  In  the  engines  of  New- 
sham  and  others,  two  cylinders,  constructed  like  forcing  pumps, 
are  worked  by  the  reciprocating  motions  of  transverse  levers, 
to  which  the  handles  are  attached.  In  this  way  the  water  is 
forced  into  the  air  vessel,  from  which  it  afterwards  spouts 
through  a  moveable  pipe.  In  some  other  engines  a  single  cy- 
linder is  used,  the  piston  rod  passing  through  a  tight  collar,  as 
it  does  in  Watt's  steam  engine,  thus  •  alternately  receiving 
and  expelling  the  water  at  each  end  of  the  cylinder.  In  Rown- 
tree's  engine,  and  some  others,  a  mechanism  is  used  like  that  of 
the  rolling  pump,  a  part  of  the  inside  of  a  cylinder  being  trav- 
ersed by  a  partition  like  a  door  hinged  upon  the  axis  of  the 
cylinder,  which  drives  the  water  successively  from  each  side 
of  the  cylinder,  into  the  air  vessel. 

A  long,  flexible  tube,  made  of  leather,  and  known  among 
firemen  by  the  name  of  hose^  is  of  great  use  in  carrying  the 
spouting  orifice  near  to  the  flames,  and  thus  preventing  the  wa- 
ter from  being  scattered  too  soon.  It  also  serves  an  important 
purpose  in  bringing  water  from  distant  reservoirs,  by  suction 
created  in  the  pumps  of  the  engine. 

Throwing  Wheel. — A  throwing  wheel,  otherwise  called  a 
flash  wheel,  or  fen  wheel,  is  used  for  raising  water,  both  by 
lifting  and  projecting  it.  Its  structure  resembles  that  of  an  un- 
dershot water  wheel,  or  more  properly  of  a  breast  wheel.  Its 
under  surface  is  received  in  a  trough  or  channel,  which  curves 
upward.  When  the  wheel  is  made  to  revolve,  it  drives  the 
water  before  it,  and  throws  it  out  from  the  trough  at  a  consid- 
erable elevation.  These  wheels  are  used  for  draining  ponds, 
marshes,  &c.,  and  are  turned  by  windmills,  or  any  other  power. 
If  their  movement  is  slow,  they  simply  lift  the  water,  and  cause 
it  to  overflow  at  the  end  of  the  trough.  But  if  they  revolve 
with  much  velocity,  they  are  capable  of  throwing  the  water  to 
a  still  higher  level. 


ARTS  OF  CONVEYING  WATER. 


327 


Robison's  Mechanical  Philosophy,  Articles  Theory  of  Rivers, 
Water  Works,  &c. ; — Gregory's  Mechanics,  vol.  i. ; — Youwg's  Nat- 
ural Philosophy,  vol.  i. ; — Bossut  TraiU  Theoretique  ei Experimental 
d'  Hydrodynamique,  1771,  &c; — Du  Boat  TraiU  d'  Hydraulique,  et 
Pyrodynamique,  1786,  &c.; — Venturi,  R^cherches  Experimentales  sur 
les  Fluides,  1797; — Rees's  Cyclopedia,  article  Water; — Edinburgh 
Encyclopedia,  article  Hydrodynamics  ; — And  the  Hydraulic  Works  of 
Mariotte,  Gdglielmini,  MicHELOTTi,  D.  and  J.  Bernoulli,  D' 
Alembert,  Fojvtana,  M.  Young,  Prony,  Vince,  Juan,  Eytel- 

WEIN,  &c. 


CHAPTER  XIV. 


ARTS  OF  DIVIDING  AND  UNITING  SOLID  BODIES. 

Cohesion. — The  attraction  of  cohesion,  which  retains  to- 
gether the  particles  of  solid  bodies,  is  the  foundation  of  their 
strength.  It  exists  in  all  solids,  though  in  different  degrees  ; 
and  requires,  before  it  can  be  overcome,  the  application  of  force 
or  of  art,  adapted  to  the  strength  and  character  of  the  particu- 
lar body.  In  some  substances,  cohesion,  when  once  overcome, 
cannot  be  reproduced  in  its  original  state.  In  others  it  may 
l)e  restored  by  the  intervention  of  fluidity,  and  in  all,  its  effects 
may  be  imitated  by  mechanical  arrangements.  The  various 
modes  by  which  bodies  maybe  divided,  or  united,  have  an  im- 
portant agency  in  mechanical  constructions,  and  other  processes 
of  art. 

MODES  OF  DIVISION. 

Fracture. — The  simplest  and  least  artificial  mode  by  which 
mechanical  division  is  effected,  is  by  breaking.  The  circum- 
stances which  influence  the  production  of  fracture  by  extension, 
compression,  lateral  strain,  and  torsion,  have  been  considered 
in  the  second  chapter  of  this  work.  In  general,  a  force  acting 
suddenly  is  more  liable  to  occasion  fracture,  than  one  which 
acts  more  gradually  ;  for  in  this  case  the  parts  which  are  first 
strained  may  give  way,  before  the  stress  is  proportionally  dis- 
tributed among  the  remaining  parts.  A  mass  of  plastic  clay, 
or  of  warm  sealing  wax,  will  bear  to  be  gradually  bent,  but 
will  break  if  the  motion  is  sudden.  In  like  manner  percussion 
occasions  fracture  more  readily  than  pressure.  A  crack,  or 
partial  fracture,  in  a  body,  greatly  promotes  the  separation  of 


ARTS  OF  DIVIDING  AND  UNITING  SOLID  BODIES.  329 

the  remainder,  whenever  a  lateral  force  is  applied  ;  because 
the  strength  of  the  sound  parts  tends  to  throw  the  strain  more 
immediately  upon  the  weakened  points,  as  explained  on  page  47. 

Cutting. — Cutting  instruments  act,  in  dividing  bodies,  upon 
the  same  principle  as  the  wedge.  The  blade  of  the  instrument 
is  in  general  a  thin  wedge,  but  the  edge  itself  is  usually  much 
more  obtuse.  Mr  Nicholson  has  estimated  the  angle  which  is 
formed  ultimately  by  the  finest  cutting  edge,  at  about  56  de- 
grees. If  the  edge  of  an  instrument  were  not  angular, 
but  rounded  or  square,  it  would  still  act  as  a  wedge,  by  push- 
ing before  it  a  wedge-shaped  portion  of  the  opposing  particles, 
as  is  done  by  obtuse  bodies  moving  in  fluids.  In  general  an 
oblique  motion  is  more  favorable  to  cutting  than  a  direct,  and 
this  is  because  the  edges  of  steel  instruments  are  rough  with 
minute  asperities,  like  sawteeth.  This  circumstance, however, 
is  of  less  importance  when  the  material  operated  upon  is  very 
firm  and  the  cutting  is  deep;  for  in  this  case  the  friction  and 
compression  consume  more  force,  than  the  actual  division. 
This  takes  place  with  axes  and  chisels,  which  are  necessarily 
made  thick  to  secure  the  requisite  strength. 

The  quality  in  tools  which  is  called  temper^  is  opposed  to 
brittleness  on  the  one  hand  and  to  flexibility  on  the  other.  In- 
dependently of  the  quality  of  the  metal,  it  appears  to  be  some- 
what influenced  by  temperature,  since  axes  and  other  tools, 
are  liable  to  break,  or  gap,  in  frosty  weather,  and  razors  cut 
best  after  being  immersed  in  hot  water. 

The  kind  of  cutting  which  is  performed  by  scissors,  depends 
upon  the  process  called  detrusion,  in  which  the  coherent  parti- 
cles are  pushed  by  each  other  in  opposite  directions.  In  this 
case  the  cutting  edges  require  to  be  angular,  but  the  angle  not 
very  acute.  The  shearing  of  woollen  cloths,  the  slitting  and 
punching  of  metals,  the  cutting  of  nails,  and  various  other  me- 
chanical processes,  are  performed  on  this  principle. 

Cutting  Machines. — A  variety  of  fibrous  and  woody  sub- 
stances, used  by  druggists  and  dyers,  require  to  be  reduced  to 
a  coarse  powder  like  saw  dust,  to  facilitate  the  extraction  of 
42 


330 


ARTS  OF  DIVIDING  AND  UNITING  SOLID  BODIES. 


their  soluble  matter.  This  is  not  easily  done  in  any  of  the 
common  mills,  owing  to  the  toughness  of  the  material.  It  is 
sometimes  effected  by  machinery  with  circular  rasps  or  saws, 
but  a  more  economical  application  of  a  dividing  force  in  these 
cases,  is  obtained  by  the  rapid  revolutions  of  a  sharp  cutting 
instrument.  In  a  machine  for  cutting  straw,  a  number  of  blades 
revolve  upon  an  axis,  with  a  fly.  In  Bramah's  surface  planing 
machinery,  and  in  Blanchard's  ingenious  engine  for  cutting  de- 
finite forms  by  a  pattern,  sharp  instruments  of  different  forms, 
are  made  to  revolve  upon  axles,  or  slide  in  grooves,  while  the 
material  operated  on  is  put  in  motion,  so  as  to  place  itself  in 
the  proper  position  to  receive  the  cut. 

Penetration. — Bodies  are  penetrated  either  by  pushing 
aside  a  portion  of  their  substance,  as  in  driving  a  nail ;  or  by 
removing  a  portion,  as  in  boring  and  drilling.  In  addition  to 
the  force  of  cohesion,  the  resistance  opposed  by  a  solid,  or 
even  by  a  soft  substance,  to  the  motion  of  a  body  tending  to 
penetrate  it,  appears  to  resemble  in  some  measure,  the  force  of 
friction,  which  is  nearly  uniform,  whether  the  motion  be  slow 
or  rapid,  destroying  a  certain  quantity  of  momentum  in  a  cer- 
tain time,  whatever  the  whole  velocity  may  be,  or  whatever 
may  be  the  space  described.  Hence  arises  an  advantage  in 
giving  a  great  velocity  to  a  body  which  is  to  penetrate  another, 
since  the  distance  to  which  a  body  penetrates  will  be  nearly  as 
the  square  of  its  velocity.  ^  The  same  remark  applies  equally 
to  the  action  of  cutting  instruments.  The  effect  of  a  hammer 
in  driving  a  nail,  depends  partly  on  the  influence  of  velocity  in 
modifying  friction,  and  partly  upon  the  momentum  accumulated 
in  the  hammer,  the  effect  of  which  resembles  that  of  a  fly 
wheel. 

Boring  and  Drilling. — The  processes  of  boring  and  drill- 
ing, performed  by  gimlets,  augers,  centrebits,  drills,  &ic.,  is  a 
species  of  circular  cutting,  in  which  a  cylindrical  portion  of 
the  substance  is  gradually  removed.    Drills  are  made  to  turn 

*  See  Young's  Natural  Philosophy,  vol.  i.  p.  225,  and  Playfaii's  vol.i.  p.  97' 


y 

ARTS  OF  DIVIDING  AND  UNITING  SOLID  BODIES.  331 

rapidly,  either  in  one  direction  by  means  of  a  lathe  wheel  and 
pulley,  or  alternately  in  opposite  directions,  by  a  spiral  cord 
which  coils  and  uncoils  itself  successively  upon  the  drill,  and  is 
aided  by  a  weight  or  fly.  In  boring  cannon  the  tool  is  at  rest, 
while  the  cannon  revolves,  and  by  this  arrangement  the  bore  of 
the  cannon  is  formed  with  more  accuracy  than  according  to  the 
old  method  of  putting  the  borer  in  motion,  perhaps  because 
the  inertia  of  so  large  a  mass  of  matter,  assists  in  defining  the 
axis  of  the  revolution  with  more  accuracy.  The  borer  is  kept 
pressed  against  the  cannon  by  a  regular  force.  Cylinders  of 
steam  engines  are  cast  hollow  and  afterwards  bored,  but  in  this 
case  the  borer  revolves,  and  the  cylinder  remains  at  rest.  In 
either  case  it  is  important  that  the  axis  of  the  borer,  and  that  of 
the  cylindrical  material,  should  coincide  ;  for  when  it  is  other- 
wise, if  the  borer  revolves,  it  will  perforate  obliquely,  and  if  the 
material  revolves,  the  perforation  will  be  conical. 

Turning. — Turning  is  an  elegant  operation,  used  to  produce 
regular  figures,  the  section  of  which  is  circular.  Like  boring, 
it  is  a  species  of  circular  cutting,  and  is  performed  in  a  well 
known  machine  called  a  lathe,  in  which  the  material  to  be  cut 
revolves  about  its  axis,  while  the  tool  is  kept  stationary  and 
supported  by  a  rest.  Besides  circular  forms,  it  may  also  be 
used  to  produce  regular  curvilinear  figures,  which  may  be  mul- 
tiplied indefinitely.  The  effect  of  most  lathes  of  complicated 
construction,  depends  on  a  certain  degree  of  motion,  of  which 
the  axis  is  capable.  If  this  motion  be  governed  by  a  frame 
producing  an  elliptic  curve,  any  number  of  ovals,  having  the 
same  centre  may  be  described  at  once  ;  and  if  a  moveable 
point  connected  with  the  work,  be  pressed  by  a  strong  spring 
against  a  pattern  of  any  kind,  placed  at  one  end  of  the  axis,  a 
copy  of  the  same  form  may  be  made  at  the  other  end  of  the 
axis.  Geometrical  lathes,  governed  by  eccentric  wheels,  and 
capable  of  describing  an  indefinite  variety  of  complex  figures, 
upon  a  metallic  plate,  are  used  for  bank-notes  and  ornamental 
designs. 


332       ARTS  OF  DIVIDING  AND  UNITING  SOLID  BODIES. 

Attrition, — The  action  of  files,  rasps,  grindstones,  and  hones, 
consists  in  successively  cutting  or  breaking  away  minute  parti- 
cles from  the  surface  of  bodies.  They  are  used  chiefly  for 
wearing  off  portions  of  hard  substances,  particularly  metals. 
The  surface  of  grindstones  and  whetstones,  is  kept  moist  with 
water  or  oil,  the  use  of  which  is  not  so  much  to  obviate  the 
production  of  heat  by  friction,  as  to  prevent  the  adhesion 
of  foreign  particles  from  filling  up  the  interstices  of  the  grit. 
In  the  finer  kinds  of  grinding  and  polishing,  certain  hard  sub- 
stances are  used  in  the  form  of  powder,  such  as  emery,  tripoli, 
sand,  putty,  oxide  of  iron,  &z;c. 

Sawing. — Saw  Mill. — A  saw,  in  many  respects,  resembles 
a  rasp,  and  acts  by  cutting  or  breaking  away  large  particles  in 
the  direction  of  its  own  plane.  The  thinner  the  saw  is,  the 
easier  is  the  operation,  since  a  smaller  amount  of  substance  is 
removed  by  the  teeth.  For  the  sake  of  this  advantage,  and 
for  economy  of  the  material,  the  blades  of  saws  are  made  thin, 
and  often  stretched  upon  frames,  to  compensate  the  want  of 
rigidity.  Saw  mills  erected  for  cutting  logs  into  boards,  con- 
sist usually  of  saws  attached  to  frames  which  have  a  reciprocat- 
ing motion  communicated  to  them  by  a  crank  connected  with 
a  water  wheel  or  steam  engine.  A  ratchet  wheel  is  connected 
with  the  saw  by  means  of  a  bar  and  click ;  so  that  at  every  stroke 
of  the  saw,  the  wheel  is  turned  the  length  of  one  tooth.  The 
ratchet  wheel  acts  by  means  of  a  rack,  upon  a  carriage,  which 
supports  the  log,  causing  it  slowly  to  advance,  until  the  whole 
length  of  the  log  has  past  the  saw. 

Circular  Saw. — Circular  saws,  revolving  upon  an  axis,  have 
the  advantage  that  they  act  continually  in  the  same  direction, 
and  no  force  is  lost  by  a  backward  stroke.  They  also  are  sus- 
ceptible of  much  greater  velocity  than  the  reciprocating  saws, 
an  advantage  which  enables  them  to  cut  more  smoothly.  The 
size  of  circular  saws,  however,  is  limited;  for,  if  made  too  large, 
and  of  the  usual  thinness,  they  are  liable  to  waver,  and  bend 
out  of  their  proper  plane;  and  on  the  other  hand  if  made 
thick  enough  to  secure  an  adequate  degree  of  strength,  they 


ARTS  OF  DIVIDING  AND  UNITING  SOLID  BODIES.  333 

wasta  both  the  power  and  the  material,  by  cutting  away  too 
much.  Hence  they  are  not  commonly  applied  to  the  slitting  of 
large  timber,  but  are  nevertheless  very  useful  in  smaller  works, 
for  cutting  off  bodies,  which  can  be  included  within  a  certain 
distance  of  the  axis,  and  thus  allow  the  saw  to  be  of  small 
size.  Circular  saws,  however,  of  large  size,  are  used  in  cut- 
ting thin  layers  of  mahogany  for  veneering ;  for  in  this  case 
the  saw  can  be  strengthened  by  thickening  it  on  one  side  to- 
wards the  centre,  the  flexibility  of  the  layer  of  wood  allowing 
it  to  turn  aside,  as  fast  as  it  is  sawn  off.  Circular  saws  may 
be  rendered  more  steady  by  giving  them  a  great  velocity,  so 
that  the  centrifugal  force  shall  assist  in  confining  the  saw  to  its 
proper  plane. 

The  sawing  of  marble  is  performed  by  saws  made  of  soft 
iron,  and  without  teeth.  A  quantity  of  sand  and  water  is  kept 
interposed  between  them,  and  the  sand,  becoming  partly  im- 
bedded in  the  iron,  serves  to  grind  away  the  marble.  These 
saws  are  worked  horizontally  for  the  convenience  of  retaining 
the  sand,  and  are  moved  either  by  hand,  or  by  reciprocating 
machinery.  The  cylindrical  blocks  which  form  the  tambours, 
or  frusta,  of  columns,  are  sometimes  cut  out  of  marble,  by 
perforating  the  block  at  the  centre,  and  inserting  an  iron  axis, 
to  the  ends  of  which  are  attached  frames,  upon  which  a  narrow, 
or  a  concave  saw  is  stretched  parallel  to  the  axis.  An  alternat- 
ing motion  is  then  given  to  the  frame,  until  the  saw  has  cut  its 
way  round  the  axis. 

Crushing. — When  materials  require  to  be  broken  into  minute 
parts,  or  when  the  texture  of  vascular  substances  is  to  be  destroy- 
ed, that  they  may  yield  their  fluid  contents,  the  operation  of 
crushing  is  resorted  to.  It  is  performed  either  by  percussion 
with  hammers,  stampers,  and  pestles,  or  by  simple  pressure 
with  weights,  rollers,  and  runner  stones. 

Stamping  Mill. — For  reducing  the  ores  of  metals  to  pow- 
der, a  number  of  heavy  vertical  bars,  called  stampers,  are  al- 
ternately raised,  and  suffered  to  fall,  by  the  action  of  cams, 
or  wipers,  projecting  from  the  arbor  of  the  mill  wheel. 


334       ARTS  OF  DIVIDING  AND  UNITING  SOLID  BODIES. 


The  ore  is  placed  in  a  trough  or  mortar  beneath,  where  it  is 
acted  upon  by  the  stampers  until  it  is  sufficiently  comminuted. 
A  stream  of  water  continually  runs  through  the  stamping 
trough,  carrying  with  it  the  particles,  which  have  become  fine 
'enough  to  pass  through  a  screen  provided  for  the  purpose. 

Bark  Mill. — The  bark  used  by  tanners  is  reduced  to  a 
coarse  powder  in  various  ways.  One  of  the  most  common 
methods,  is  to  crush  the  bark  by  the  revolutions  of  a  circular 
stone,  called  a  runner  stone,  which  resembles  the  wheel  of  a 
carriage,  travelling  round  in  a  continued  circuit.  The  axis  of 
the  stone  is  connected  with  a  vertical  shaft,  so  that  the  stone  has 
two  motions,  one  round  its  own  axis,  which  is  horizontal,  and 
the  other  round  the  vertical  shaft.  The  bark  is  raked  up  into 
a  ridge  before  the  stone,  and  is  crushed  or  ground  up,  by  the 
-edge  of  the  stone  rolling  over  it.  In  some  more  complicated 
mills,  the  bark  is  successively  cut  with  knives,  beaten  with 
hammers,  and  ground  with  stones,  or  cylinders. 

Oil  Mill. — The  oleaginous  seeds  from  which  oil  is  express- 
ed, require  to  have  their  substance  previously  broken  up  by 
the  operations  of  a  mill.  In  one  of  the  best  forms  of  the  oil 
mill,  the  seeds  are  first  bruised  to  the  consistence  of  paste,  by 
the  action  of  runner  stones.  The  paste  is  received  in  troughs 
perforated  with  holes,  through  which  a  portion  of  the  oil  drips, 
and  this  part  is  considered  the  most  pure.  The  paste  is  then 
put  into  strong  bags  and  subjected  to  pressure,  as  long  as  it 
yields  oil.  The  remaining  paste,  or  oil  cake,  is  next  taken  out 
of  the  bags,  broken  to  pieces,  and  put  into  mortars.  It  is  here 
beaten  by  the  action  of  heavy  stampers  until  reduced  to  a  very 
minute  state  of  subdivision.  The  oil  which  is  next  pressed  out 
from  it  is  inferior  in  quality  to  the  first,  in  consequence  of  its 
containing  more  mucilage  and  farinaceous  particles.  The 
seeds  are  nevertheless  subjected  to  another  pressure,  after 
having  been  exposed  to  heat,  which  enables  them  to  yield  a 
quantity  more  of  oil,  but  of  a  still  poorer  quality. 

Sugar  Mill. — The  machine  by  which  sugar  canes  are 
crushed,  usually  consists  of  three  vertical  rollers,  the  middle 


ARTS  OF  DIVIDING  AND  UNITING  SOLID  BODIES. 

one  of  which  is  turned  by  a  horse,  or  other  power,  and  turns 
the  remaining  two  by  friction,  or  by  toothed  wheels ;  the  latter 
method  being  most  advantageous.  The  canes  are  supplied  by 
attendants,  and  are  drawn  in  and  crushed  between  the  first  and 
second  rollers,  after  which  they  return  and  pass  between  the 
second  and  third.  The  juice  which  is  pressed  out  by  the  same 
operation,  flows  into  a  trough  beneathr 

Cider  Mill. — When  the  substances  to  be  crushed  are  so- 
large  that  they  cannot  readily  be  drawn  in  between  smooth 
cylinders,  it  is  necessary  that  the  rollers  should  be  indented  at 
their  circumference.  The  common  cider  mill  is  formed  with, 
two  indented  cylinders,  the  teeth  of  one  of  which  enter  the  in- 
dentations of  the  other.  By  this  arrangement  the  fruit  to  be 
ground  is  caught  by  the  projecting  parts  of  the  rollers  and  reg- 
ularly carried  forward  and  crushed.  Formerly  it  was  the 
custom  to  grind  apples  by  runner  stones,  similar  to  those  used 
in  bark  mills.  And  at  the  present  day  cylindrical  rasps  are 
sometimes  employed,  being  supposed  capable  of  destroying 
the  texture  of  the  fruit  more  effectually. 

Grinding. — Grinding,  in  its  most  limited  sense,  may  be  con- 
sidered as  a  species  of  crushing,  or  breaking,  in  which  the  force 
acts  partly  in  a  lateral  direction,  so  as  to  lacerate,  rather  than 
compress  the  material  acted  upon.  It  is  frequently  produced 
in  small  mills,  by  a  cylinder  or  cone,  turning  within  another 
which  is  hollow,  the  surfaces  of  both  being  cut  obliquely  into 
teeth.  In  larger  mills  it  is  commonly  performed  by  one  stone 
moving  upon  another. 

Grist  Mill. — The  common  mill  for  grinding  grain,  is  con- 
structed with  two  circular  stones  placed  horizontally.  Buhr- 
stone  is  the  best  material  of  which  mill  stones  are  made,  but 
sienite  and  granite  are  frequently  used,  for  indian  corn  and  rye. 
The  lower  stone  is  fixed,  while  the  upper  one  revolves  with 
considerable  velocity,  and  is  supported  by  an  axis  passing 
through  the  lower  stone,  the  distance  between  the  two  being 
capable  of  adjustment  according  to  the  fineness  which  it  is  in- 
tended to  produce  in  the  meal,  or  flour.    When  the  diameter 


336       ARTS  OF  DIVIDING  AND  UNITING  SOLID  BODIES. 

is  five  feet,  the  stone  may  make  about  90  revolutions  in  a  min- 
ute without  the  flour  becoming  too  much  heated.  The  corn 
or  grain  is  shaken  out  of  a  hopper  by  means  of  projections 
from  the  revolving  axis,  which  give  to  its  lower  part  or  feeder, 
a  vibrating  motion.  The  lower  stone  is  slightly  convex,  and 
the  upper  one  somewhat  more  concave,  so  that  the  corn  which 
enters  at  the  middle  of  the  stone,  passes  outward  for  a  short 
distance  before  it  begins  to  be  ground.  After  being  reduced 
to  powder,  it  is  discharged  at  the  circumference,  its  escape  be- 
ing favored  by  the  centrifugal  force,  and  by  the  convexity  of 
the  lower  stone.  The  surface  of  the  stones  is  cut  into  grooves, 
in  order  to  make  them  act  more  readily  and  effectually  on  the 
corn ;  and  these  grooves  are  cut  obliquely,  that  they  may  assist 
the  escape  of  the  meal  by  throwing  it  outward.  The  opera- 
tion of  bolting,  by  which  the  flour  is  separated  from  the  bran,  or 
coarser  particles,  is  performed  by  a  cylindrical  sieve  placed  in 
an  inclined  position  and  turned  by  machinery.  The  fineness 
of  flour  is  said  to  be  greatest  when  the  bran  has  not  been  too 
much  subdivided,  so  that  it  may  be  more  readily  separated  by 
bolting.  This  takes  place  when  the  grinding  has  been  per- 
formed more  by  the  action  of  the  particles  upon  each  other, 
than  by  the  grit  of  the  stone.  For  this  sort  of  grinding,  the 
buhrstone  is  peculiarly  suited. 

Color  Mill. — The  various  coloring  substances  used  by  pain- 
ters, when  they  are  not  soluble  in  oil  or  water,  require  to  be  redu- 
ced to  an  impalpable  powder  by  grinding.  This  is  commonly 
performed  upon  a  smooth  stone  slab,  by  trituration  with  another 
stone  called  a  muUer.  When  the  grinding  is  performed  by 
machinery,  a  large  muller  of  the  shape  of  a  pear,  having  a 
groove  cut  in  it  for  the  admission  of  the  paint,  is  made  to  re- 
volve in  a  mortar,  the  bottom  of  which  is  of  a  corresponding 
shape.  In  some  color  mills  a  horizontal  stone  cyhnder  revolves  ' 
in  contact  with  another  stone,  which  is  concave,  and  covers  a 
part  of  its  convex  surface.  In  most  cases  the  substance  to  be 
ground  is  mixed  with  oil  or  water..  As  some  of  the  substances 
used  for  pigments  are  of  a  poisonous  character,  they  should  be 
ground  in  close  cavities,  or  under  water. 


ARTS  OF  DIVIDING  AND  UNITING  SOLID  BODIES. 


337 


MODES  OF  UNION. 

Insertion. — The  mechanical  modes  of  attaching  bodies  to 
each  other,  usually  consist  in  the  insertion  of  their  parts  among 
each  other,  or  in  the  application  of  other  substances  specially 
adapted  for  the  purpose  of  connexion.  Insertion  is  performed 
by  various  modes,  the  principal  of  which  are,  1.  Mortising, 
in  which  the  projecting  extremity  of  one  timber  is  received 
into  a  perforation  in  another.  2.  Scarfing  and  interlocking,  in 
which  the  ends  of  pieces  overlay  each  other,  and  are  indented 
together  so  as  to  resist  longitudinal  strain  by  extension,  as  in  tie 
beams,  and  ends  of  hoops.  3.  Tongueing  and  rahating,  in 
which  the  edges  of  boards  are  wholly,  or  partly,  received  by 
channels  in  each  other.  4.  Dovetailing,  when  the  parts  are 
connected  by  wedge-shaped  indentations,  which  permit  them  to 
be  separated  only  in  one  direction.  5.  Linking,  where  the 
ends  of  flexible  rods  are  bent  over  each  other.  6.  Folding, 
when  the  edges  of  flexible  plates  are  connected  in  a  similar 
manner.  7.  To  these  may  be  added  the  combinations  of  flexi- 
ble fibres,  by  tying,  twisting,  weaving,  &;c.,  in  which  the  per- 
manency of  the  union  depends  upon  friction. 

Interposition. — When  two  substances  are  mechanically  unit- 
ed by  the  intervention  of  a  third,  the  latter,  from  its  smaller 
size,  should  be  made  of  the  strongest  material.  JVails  are  a 
common  connecting  medium  in  wooden  structures.  The  sta- 
bility of  a  nail  depends  upon  its  friction,  or  adhesion,  and  is 
increased  by  its  roughness,  the  smallness  of  the  angle  made  by 
its  sides,  and  the  elasticity  of  the  material  into  which  it  is 
driven. 

When  the  force  tending  to  produce  separation  is  great,  nails 
do  not  afford  an  adequate  security.  In  such  cases,  it  is  com- 
mon to  employ  screws,  which  are  inserted  by  the  force  of  tor- 
sion and  cannot  be  withdrawn  by  that  of  extension,  while  the 
material  is  sound.  Where  great  strength  is  required,  holts  of 
metal  are  used,  which  pass  through  the  substances  to  be  con- 
43 


338        ARTS  OF  DIVIDING  AND  UNITING  SOLID  BODIES. 

nected,  and  are  secured  at  their  smaller  extremity  by  a  nut  and 
screw,  or  by  a  transverse  key.  Rivets  are  short  bolts,  the  two 
ends  of  which  are  headed,  or  spread  by  hammering,  after  they 
are  inserted. 

Binding. — In  some  cases  the  materials  to  be  connected  are 
not  perforated,  but  surrounded  by  the  connecting  substance. 
Hoops  and  bands  of  metal,  wood,  and  flexible  fibres,  are  used 
for  this  purpose.  Incases  where  it  is  applicable,  binding  ordi- 
narily affords  the  strongest  mode  of  connexion,  but  is  attended  • 
with  the  greatest  expenditure  of  the  connecting  material. 

Locking, — For  the  temporary  connexion  of  parts,  which 
requires  to  be  often  repeated,  latches,  bolts,  hooks,  buttons,  and 
locks  are  employed.  Of  these  the  lock  is  the  only  one  whose 
structure  is  at  all  complicated.  The  principle  upon  which 
locks  depend,  is  the  application  of  a  lever  to  an  interior  bolt, 
by  means  of  a  communication  from  without.  The  lever  is  the 
key,  and  the  bolt  receives  from  it  a  progressive  motion  in  either 
direction.  The  security  of  a  lock  depends  upon  the  number 
of  obstacles  which  can  be  interposed  between  the  movement  of 
the  bolt,  and  the  action  of  any  instrument,  except  the  proper 
key.  The  luards  of  locks  are  impediments  of  this  kind,  and  to 
enable  the  key  to  pass  them,  certain  portions  of  its  substance 
are  cut  away.  Various  complicated  and  difficult  locks  have 
been  constructed  by  Messrs  Bramah,  Taylor,  Spears,  and 
others.  In  a  very  ingenious  lock  invented  by  Mr  Perkins, 
twentyfour  small  blocks  of  metal  of  different  sizes  are  introduc- 
ed, corresponding  to  the  letters  of  the  alphabet.  Out  of  these 
an  indefinite  number  of  combinations  may  be  made.  The 
person  locking  the  door,  selects,  and  places,  the  blocks  neces- 
sary to  spell  a  particular  word  known  only  to  himself,  and  no 
other  person,  even  if  in  possession  of  the  key,  can  open  the 
door,  without  a  knowledge  of  the  same  word. 

Cementing. — Cements  are,  for  the  most  part,  soft  or  semi- 
fluid substances,  which  have  the  property  of  becoming  hard  in 
time,  and  cohering  with  other  bodies  to  which  they  have  been 
applied.    A  variety  of  these  substances  are  used  for  uniting 


ARTS  OF  DIVIDING  AND  UNITING  SOLID  BODIES.  339 

different  materials.  The  compounds  of  lime  and  sand,  which 
constitute  the  ordinary  building  cements,  have  been  considered 
in  Chapter  First.  For  uniung  pieces  of  marble,  plaster  of  Par- 
is dried  by  heat,  and  mixed  with  water,  or  with  rosin  and  wax, 
is  employed.  A  cement  for  iron  is  made  by  mixing  sulphur 
and  muriate  of  ammonia  with  a  large  quantity  of  iron  chippings. 
This  is  used  for  the  joints  of  iron  pipes,  and  the  flanges  of 
steam  engines.  Turners,  and  some  other  mechanics,  confine 
the  material  on  which  they  are  working,  by  a  cement  composed 
of  brickdust  and  rosin,  or  pitch.  The  cement  used  by  glaziers, 
under  the  name  of  putty,  is  a  mixture  of  linseed  oil  and  pow- 
dered chalk.  China  ware  is  cemented  by  common  paint, 
made  of  white  lead  and  oil,  or  by  resinous  substances,  such  as 
mastic  and  shell  lac,  or  by  isinglass  dissolved  in  proof  spirit  or 
water.  Bookbinders,  and  paper  hangers,  employ  ^a^^e,  made 
by  boiling  flour,  and  a  similar  but  more  elegant  article  under 
the  name  of  rice  glue,  is  prepared  by  boiling  ground  rice  in 
soft  water  to  the  consistence  of  a  thin  jelly.  Wafers  are  made 
of  flour,  isinglass,  yeast,  and  white  of  eggs,  dried  in  thin  strata 
upon  tin  plates,  and  cut  by  a  circular  instrument.  The  color 
is  given  by  red  lead,  and  other  pigments.  Sealing  wax  is 
composed  of  shell  lac  and  rosin,  and  is  commonly  colored  with 
vermilHon. 

Glueing. — For  uniting  wood  and  similar  porous  substances, 
common  glue  takes  precedence  of  all  other  cements.  It  is 
dissolved  by  heating  it  with  water,  and  is  applied  with  a  brush 
to  both  the  surfaces  to  be  united.  Glue  does  not  adhere  so 
readily,  if  the  surfaces  be  in  the  least  oily,  or  if  a  coating  of  old 
glue  is  previously  upon  them,  or  indeed  if  the  pores  are  filled 
with  any  foreign  substance.  The  cementing  power  of  glue 
depends  upon  the  strength  which  it  possesses  when  dry,  and 
the  hold  which  it  obtains  upon  the  wood,  by  penetrating  its 
pores.  It  does  not  furnish  a  suflicient  bond  of  union  for  surfa- 
ces which  are  not  porous,  as  those  of  metals ;  and  it  is  not  du- 
rable when  exposed  to  the  action  of  water. 


340        ARTS  OF  DIVIDING  AND  UNITING  SOLID  BODIES. 

TV dding. — Certain  metals,  such  as  iron  and  platinum,  which 
are  exceedingly  difficult  of  fusion,  are  capable  of  being  united 
by  the  process  of  welding.  This  consists  in  hammering  them 
together  while  they  are  at  a  very  high  temperature.  Bar  iron 
cannot  be  welded  without  raising  it  to  a  heat  of  nearly  60  de- 
grees of  Wedgewood's  pyrometer.  Cast  steel  would  be  melted 
at  this  temperature,  and  therefore  in  welding  iron  to  steel,  the 
steel  is  raised  only  to  a  common  white  heat.  Care  is  taken  to 
prevent  the  surfaces  which  are  to  be  welded  from  being  oxi- 
dized too  much,  or  else  to  detach  the  scales  w^ien  the  metal  is 
brought  to  a  welding  heat.  The  union  of  welded  pieces  probably 
depends  on  an  incipient  fusion  of  their  surfaces.  When  prop- 
erly conducted,  the  metal  is  supposed  to  be  as  strong  in  the 
welded  part,  as  in  any  other. 

Soldering. — The  process  of  soldering  consists  in  uniting  to- 
gether parts  of  the  same,  or  of  different  metals,  by  the  intervention 
of  a  metallic  substance  employed  in  a  state  of  fusion.  It  is 
necessary  that  the  uniting  substance  should  melt  sooner  than 
the  substance  to  be  soldered,  that  it  should  adhere  firmly  to  its 
surface,  and  as  far  as  practicable,  approach  to  the  metal  sol- 
dered, in  hardness  and  color.  Iron  is  usually  soldered  with 
brass,  and  hence  the  process  is  commonly  called  brazing.  An 
alloy  of  tin  and  iron  is  sometimes  used  instead  of  brass  for  the 
same  purpose.  Copper  may  be  united  either  by  a  hard  solder 
made  of  brass  and  zinc,  or  a  soft  solder  composed  of  zinc  and 
lead.  Tin  is  soldered  with  pewter  made  of  tin  and  lead,  with 
sometimes  a  portion  of  bismuth.  Gold  and  silver  are  united 
with  solders  made  of  gold  or  silver,  alloyed  with  copper  or 
brass.  Platinum  is  soldered  with  gold.  The  adhesion  of 
solders  depends  upon  an  alloy  being  formed  between  the  sur- 
faces in  contact. 

As  the  oxidation  of  the  surface  of  metals  tends  to  prevent 
the  adhesion  of  the  solder,  it  is  common  to  unite  with  the  sol- 
der some  additional  substance,  which  may  obviate  this  difficul- 
ty. In  soldering  copper,  brass,  iron,  &ic.  it  is  common  to  em- 
ploy borax,  a  salt  which  fuses  at  the  time  when  the  metals 


ARTS  OF  DIVIDING  AND  UNITING  SOLID  BODIES.  341 

would  be  most  liable  to  oxidate,  and  by  enveloping  the  metallic 
surface,  prevents  the  farther  action  of  the  oxygen  of  the  atmos- 
phere. Potash,  soda,  tartar,  and  various  salts  are  used  for  the 
same  purpose.  Muriate  of  ammonia  has  a  remarkable  effect 
in  freeing  the  surfaces  of  metals  from  oxygen,  which  it  does, 
apparently,  by  combining  with  the  metallic  oxide,  and  carrying 
it  off  as  it  sublimes.  In  soldering  the  more  fusible  metals,  as 
tin  and  lead,  a  carbonaceous  substance  is  employed,  such  as 
rosin,  or  oil,  which  tends  to  cover  the  surface,  and  also  to  re- 
duce the  oxide  to  its  metallic  state,  as  fast  as  it  is  formed. 

Casting. — The  process  of  fusion,  or  melting,  affords  in 
many  substances,  the  most  effectual  method  both  of  destroying 
the  cohesion  of  their  particles,  and  of  afterwards  restoring  it 
under  new  arrangements.  Many  substances,  both  simple  and 
compound,  such  as  metals,  glass,  wax,  &;c.,  may  become 
liquid  and  again  solid,  without  essentially  changing  their  physi- 
cal qualities.  On  the  other  hand,  many  natural  bodies,  crys- 
tallized minerals,  and  organic  combinations,  cannot  be  fused 
without  changing  their  characteristic  properties.  Some  sub- 
stances are  with  difficulty  fusible  when  alone,  but  become 
more  fusible  when  combined  with  another  substance,  as  is  the 
case  of  sand  with  an  alkali,  or  iron  with  carbon.  Others  again 
have  their  fusibility  lessened  by  combination,  as  happens  in 
metals  when  they  become  oxidized. 

Fluxes. — The  name  of  fluxes  has  been  given  to  certain  sub- 
stances which  assist  fusion,  either  by  expediting  the  process,  or 
by  protecting  the  substance  melted  from  alteration.  In  separa- 
ting metals  from  their  ores,  fluxes  are  employed  to  render  the 
substances  with  which  the  metal  is  combined,  capable  of  fusion. 
Thus  if  the  ore  abound  with  siliceous  earth  or  stone,  an  alka- 
line flux,  such  as  potash,  soda,  or  tartar,  has  the  effect  of  com- 
bining with  the  siliceous  substances,  and  forming  with  them  a 
vitreous  compound,  which  floats  upon  the  top  of  the  mehed 
metal.  Tartar  also  contains  a  portion  of  vegetable  matter,  the 
carbon  and  hydrogen  of  which  serve  to  deoxidize  the  metal. 
Borax,  common  salt,  and  many  other  saline  bodies,  when  melt- 


342        ARTS  OF  DIVIDING  AND  UNITING  SOLID  BODIES. 

ed,  prevent  the  oxidation  of  metals  by  protecting  their  surface 
from  the  atmosphere.  Muriate  of  ammonia,  rosin,  fatty  sub- 
stances, powdered  charcoal,  &ic.,  prevent  or  remove  oxidation, 
by  combining  either  with  the  oxygen,  or  with  the  oxide  when 
formed. 

Moulds, — The  moulds  used  for  casting  melted  bodies  must 
be  suited  to  the  temperature  at  which  the  body  melts.  For 
metals  which  melt  at  a  high  heat,  as  copper,  brass,  cast  iron, 
&5c.,  the  moulds  are  made  of  some  refractory  substance,  such 
as  loam,  sand,  pounded  brick  with  plaster,  or  clay,  he.  Glass 
is  cast  in  moulds  made  of  copper,  but  these  require  to  be  fre- 
quently cooled.  Those  bodies  which  melt  at  temperatures  be- 
low that  of  ignition,  as  tin,  lead,  wax,  he,  may  be  cast  in 
moulds  of  any  convenient  metal,  or  of  wood,  and  other  inflam- 
mable materials. 

The  forms  of  some  bodies  may  be  changed,  and  their  sepa- 
ration or  union  effected,  without  the  agency  of  fusion,  in  vari- 
ous ways.  It  may  be  done  by  mixture  with  water,  as  in  clay 
and  plaster ;  by  solution  in  water,  as  in  glue,  rice,  and  gum ;  and 
by  sublimation,  as  in  camphor,  and  muriate  of  ammonia. 


Young's  Lectures  on  Natural  Philosophy; — Gregory's  Mechan- 
ics;— Nicholson's  Operative  Mechanic,  8vo.; — Gray's  Operative 
Chemist,  8vo.  1828 ; — Rees's  Cyclopedia,  and  Brewster's  Edinburgh 
Encyclopedia,  under  various  heads. 


CHAPTER  XV. 


ARTS  OF  COMBINING  FLEXIBLE  FIBRES. 

Theory  of  Tivisting. — The  strength  of  cordage,  which  is 
employed  in  uniting  bodies,  and  the  utility  of  flexible  textures, 
which  serve  for  furniture  or  for  clothing,  depend  principally 
upon  the  friction  or  lateral  adhesion,  produced  by  the  twisting 
and  intermixture  of  their  constituent  fibres. 

A  twisted  cord  is  not  so  strong  as  the  fibres  which  compose 
it,  supposing  the  fibres  and  cord  to  be  of  the  same  length.  The 
object  of  twisting  is  to  connect  successive  numbers  of  short 
fibres  in  such  a  manner,  that,  besides  the  mutual  pressure  which 
their  own  elasticity  causes  them  to  exert,  any  additional  force 
applied  in  the  direction  of  the  length  of  the  aggregate,  may 
tend  to  bring  their  parts  into  closer  contact,  and  augment  their 
adhesion  to  each  other.  The  simple  art  of  tying  a  knot,  and 
the  more  complicated  processes  of  spinning,  rope  making,  weav- 
ing, and  felting,  derive  most  of  their  utility  from  this  principle. 

By  considering  the  effect  of  a  force  which  is  counteracted 
by  other  forces  acting  obliquely,  it  will  be  seen  that  the  opera- 
tion of  twisting  has  a  useful  effect  in  binding  the  parts  of  a 
rope  or  thread  together,  and  also  that  it  has  an  inconvenience 
in  causing  the  strength  of  the  fibres  to  act  with  a  mechanical 
disadvantage.  The  greater  is  the  obliquity  of  the  fibres,  the 
greater  will  be  their  adhesion  to  each  other,  but  the  greater  also 
will  be  their  immediate  strain  or  tension,  when  a  force  acts  upon 
them  in  the  direction  of  the  whole  cord.  From  this  it  follows 
that  after  employing  as  much  obliquity  and  as  much  tension  as 
is  sufficient  to  connect  the  fibres  firmly  together,  all  that  is  su- 
perfluously added  tends  to  weaken  the  cord,  by  overpowering  the 
primitive  cohesion  of  the  fibres  in  the  direction  of  their  length. 


344 


ARTS  OP  COMBINING  FLEXIBLE  FIBRES. 


The  mechanism  of  simple  spinning  is  easily  understood. 
Care  is  taken,  where  the  hand  is  employed,  to  intermix  the 
fibres  sufficiently,  and  to  engage  their  extremities  as  much  as 
possible  in  the  centre ;  for  it  is  obvious,  that  if  any  fibre  were 
wholly  external  to  the  rest,  it  could  not  be  retained  in  the  yarn. 
In  general,  however,  the  materials  are  previously  in  such  a  state 
of  intermixture  as  to  render  this  precaution  unnecessary. 

Rope  Making. — A  single  thread  of  yarn,  consisting  of  fibres 
twisted  together,  has  a  tendency  to  untwist  itself,  the  external 
parts  being  strained  by  extension,  and  the  internal  parts  by 
compression ;  so  that  the  elasticity  of  all  the  parts  resists,  and 
tends  to  restore  the  thread  to  its  natural  state.  But  if  two 
such  threads  similarly  twisted,  are  retained  in  contact  at  a  given 
point  of  the  circumference  of  each,  this  point  is  rendered  sta- 
tionary by  the  opposition  of  the  equal  forces  acting  in  contrary 
directions,  and  becomes  the  centre,  round  which  both  threads 
are  carried  by  the  forces  which  remain,  so  that  they  continue 
to  twist  round  each  other,  till  the  new  combination  causes  a 
tension,  capable  of  counterbalancing  the  remaining  tension  of 
the  original  threads.  Three,  four,  or  more  threads,  may  be 
united  nearly  in  the  same  manner.  A  strand,  as  it  is  called  by 
rope  makers,  consists  of  a  considerable  number  of  yarns  thus 
twisted  together,  generally  from  sixteen  to  twentyfive ;  a  haw- 
ser consists  of  three  strands,  a  shroud  of  four,  and  a  cahle  of 
three  hawsers  or  shrouds.  Shroud  laid  cordage  has  the  dis- 
advantage of  being  hollow  in  the  centre,  or  else  of  requiring  a 
great  change  of  form  in  the  strands  to  fill  up  the  vacuity,  so 
that  in  undergoing  this  change,  the  cordage  stretches,  and  is 
unequally  strained.  The  relative  position  and  the  comparative 
tension  of  all  the  fibres  in  these  complicated  combinations  are 
not  very  easily  determined  by  calculation ;  but  it  is  found  by 
experience  to  be  most  advantageous  for  the  strength  of  ropes, 
to  twist  the  strands,  when  they  are  to  be  compounded,  in  such 
a  direction  as  to  untwist  the  yarns  of  which  they  are  formed  ; 
that  is,  to  increase  the  twist  of  the  strands  themselves  ;  and 
probably  the  greatest  strength  is  obtained  when  the  ultimate 


ARTS  OF  COMBINING  FLEXIBLE  FIBRES.  345 


obliquity  of  the  constituent  fibres  is  least,  and  the  most 
equable.  * 

A  very  strong  rope  may  also  be  made  by  twisting  five  or  six 
strands  round  a  seventh  as  an  axis.  In  this  case  the  central 
strand,  or  heart,  is  found  after  much  use  to  be  chafed  to  oakum. 
Such  ropes  are,  however,  considered  unfit  for  rigging,  or  for 
any  use  in  which  they  are  liable  to  be  frequently  bent. 

Ropes  are  most  commonly  made  of  hemp,  but  various  other 
vegetables  are  occasionally  employed.  The  Chinese  even  use 
woody  fibres,  and  the  barks  of  trees  furnish  cordage  to  other 
nations.  In  spinning  the  yarn,  in  the  process  of  rope  making, 
the  hemp  is  fastened  round  the  waist  of  the  workman  ;  one  end 
of  it  is  attached  to  a  wheel  turned  by  an  assistant,  and  the 
spinner,  walking  backwards,  draws  out  the  fibres  with  his  hands. 
When  one  length  of  the  walk  has  been  spun,  it  is  immediately 
reeled,  to  prevent  its  untwisting.  The  machines  employed  in 
continuing  the  process  of  rope  making,  are  mostly  of  simple 
construction,  but  both  skill  and  attention  are  required  in  apply- 
ing them  so  as  to  produce  an  equable  texture  in  every  part  of 
the  rope.  The  tendency  of  two  strands  to  twist,  in  consequence 
of  the  tension  arising  from  the  original  twist  of  the  yarns,  is  not 
sufficient  to  procure  an  equilibrium,  because  of  the  friction 
and  rigidity  to  be  overcome.  Hence  it  is  necessary  to  employ 
force  to  assist  this  tendency,  and  the  strands  or  ropes  will  after- 
wards retain  spontaneously  the  form  which  has  thus  been  giv- 
en them.  The  largest  ropes  even  require  external  force  in  or- 
der to  make  them  twist  at  all. 

The  constituent  ropes  of  a  common  cable,  when  separate, 
are  stronger  than  the  cable,  in  the  proportion  of  about  four  to 
three  ;  and  a  rope  worked  up  from  yarns  180  yards  in  length, 
lo  135  yards,  has  been  found  to  be  stronger  than  when  reduced 
to  120  yards,  in  the  ratio  of  six  to  five.  The  difference  is 
owing  partly  to  the  obliquity  of  the  fibres,  and  partly  to  the 
unequal  tension  produced  by  twisting,  f 

*  Young's  Natural  Philosophy,  vol.  i.  Lect.  xvi.  i  Ibul. 

44 


346 


ARTS  OF  COMBINING  FLKXIBLE  FIBRES. 


COTTON  MANUFACTURE. 

When  the  fibres  of  cotton,  wool,  or  flax,  are  intended  to  be 
woven,  they  are  reduced,  to  fine  threads  of  uniform  size 
by  the  well  known  process  of  spinning.  Previously  to  the 
middle  of  the  last  century,  this  process  was  performed  by  hand, 
with  the  aid  of  the  common  spinning  wheel.  Locks  of  cotton 
or  wool,  previously  carded,  were  attached  to  a  rapidly  revolv- 
ing spindle  driven  by  a  large  wheel,  and  were  stretched,  or 
drawn  out  by  the  hand,  at  the  same  time  that  they  were  twist- 
ed by  the  spindle,  upon  which  they  were  afterwards  wound. 
Flax,  the  fibres  of  which  are  longer  and  more  parallel,  was 
loosely  wound  upon  a  distaff,  from  which  the  fibres  were  se- 
lected and  drawn  out  by  the  thumb  and  finger,  and  at  the  same 
time  were  twisted  by  flyers  and  wound  upon  a  bobbin,  which 
revolved  with  a  velocity  somewhat  less  than  that  of  the  flyers. 

The  manufacture  of  flexible  stuffs  by  means  of  machinery, 
operating  on  a  large  scale,  is  an  invention  of  the  last  century. 
Although  of  recent  date,  it  has  given  birth  to  some  of  the  most 
elaborate  and  wonderful  combinations  of  mechanism,  and  al- 
ready constitutes,  especially  in  England  and  in  this  country,  an 
important  source  of  national  wealth  and  prosperity. 

Elementary  Inventions. — The  character  of  the  machinery 
which  has  been  applied  to  the  manufacture  of  cotton  at  differ- 
ent times,  has  been  various.  There  are,  however,  several 
leading  inventions,  upon  which  most  of  the  essential  processes 
are  founded,  and  which  have  given  to  their  authors  a  greater 
share  of  celebrity  than  the  rest.  These  are,  1 .  The  spinning 
jenny.  This  machine  was  invented  by  Richard  Hargreaves,  * 
in  1767,  and  in  its  simplest  form  resembled  a  number  of  spin- 
dles turned  by  a  common  wheel,  or  cylinder,  which  was  work- 
ed by  hand.  It  stretched  out  the  threads  as  in  common  spinning 
of  carded  cotton.  2.  The  water  spinning  frame,  invented  by 
Richard  Arkwright,  in  1769.    The  essential  and  most  impor- 

*  Mr  Guest  in  a  late  work  attributes  the  invention  both  of  the  jenny  and 
water  spinning  frame,  to  Thomas  Highs,  of  Leigh,  England. 


ARTS  OF  COMBINING  FLEXIBLE  FIBRES. 


347 


tant  feature  in  this  invention,  consists  in  the  drawing  out,  or 
elongating  of  the  cotton,  by  causing  it  to  pass  between  succes- 
sive pairs  of  rollers,  which  revolve  with  different  velocities, 
and  which  act  as  substitutes  for  the  finger  and  thumb,  as  ap- 
plied in  common  spinning.  These  rollers  are  combined  with 
the  spindle  and  flyers  of  the  common  flax  wheel.  3.  The 
mule.  This  was  invented  by  Samuel  Crompton,  in  1779.  It 
combines  the  principles  of  the  two  preceding  inventions,  and 
produces  finer  yarn  than  that  which  is  spun  in  either  of  the 
other  machines.  It  has  now  nearly  superseded  the  jenny.  4. 
^he  power  loom  for  weaving  by  water  or  steam  power,  which 
was  introduced  about  the  end  of  the  eighteenth  century,  and 
has  received  various  modifications. 

The  foregoing  fundamental  machines  are  used  in  the  same 
or  diflerent  establishments,  and  for  different  purposes.  But 
besides  these,  various  auxiliary  machines  are  necessary  to 
perform  intermediate  operations,  and  to  prepare  the  material  as 
it  passes  from  one  stage  of  the  manufacture  to  another.  The 
number  of  these  machines,  and  the  changes  and  improvements 
which  have  been  made  in  their  construction  from  time  to  time, 
render  it  impossible  to  convey,  in  a  work  like  the  present,  any 
accurate  idea  of  their  formation  in  detail.  A  brief  view,  how- 
ever, of  the  offices  which  they  severally  perform,  may  be  tak- 
en by  following  the  raw  material  through  the  principal  changes 
which  it  undergoes  in  a  modern  cotton  factory,  founded  and 
improved  upon  the  general  principles  of  Arkwright. 

Batting. — The  cotton,  after  having  been  cleared  from  its 
seeds,  at  the  plantation,  by  the  operation  of  ginning,  described 
on  page  33,  is  compressed  into  bags  for  exportation,  and  ar- 
rives at  the  factory  in  a  dense  and  matted  mass.  The  first 
operation  to  which  it  is  submitted  has  for  rts  object  to  disentan- 
gle the  fibres,  and  restore  the  cotton  to  a  light,  open,  and  uniform 
state.  For  this  purpose,  after  being  weighed  out,  it  is  submit- 
ted to  the  operation  of  a  machine  called  a  picker,  or  of  another 
denominated  a  batter.  In  some  of  these  machines  it  is  sub- 
jected to  the  action  of  a  series  of  pins,  in  others  to  a  sort  of 


348 


ARTS  OF  COMBINING  FLEXIBLE  FIBRES. 


blunt  knives,  revolving  with  great  rapidity ;  the  effect  of  which 
is  to  beat  up  and  separate  the  fibres,  to  disengage  their  unequal 
adhesions,  and  to  reduce  the  whole  to  a  very  light,  uniform, 
flocculent  mass. 

Carding. — The  cotton  next  passes  to  the  carding  machines, 
of  which,  when  there  are  two,  the  first  is  called  the  breaker, 
and  the  second  the  finisher.  In  this  operation  the  cotton  is 
carried  over  the  surface  of  a  revolving  cylinder  which  is  cov- 
ered with  card  teeth  of  wire,  and  which  passes  in  contact  with 
an  arch,  or  part  of  a  concave  cylinder,  similarly  covered  with 
teeth.  From  this  cylinder  it  is  taken  off  by  another,  called  the 
dojjing  cylinder,  which  revolves  in  an  opposite  direction  ;  and 
from  this  it  is  again  removed  by  the  rapid  vibrating  movement 
of  a  transverse  comb,  otherwise  called  the  doffing  plate,  moved 
by  cranks.  It  then  exists  in  the  state  of  a  flat,  uniform,  fleece, 
or  lap,  which,  after  passing  the  breaker,  undergoes  the  process 
of  plying,  or  doubling,  by  causing  it  to  perform  a  certain  num- 
ber of  revolutions  upon  a  cylinder,  or  a  perpetual  cloth.  It  is 
then  carded  a  second  time,  by  the  finisher,  and  the  fleece,  after 
being  taken  off  from  this  machine,  is  drawn  by  rollers  through 
a  hollow  cone,  or  trumpet  mouth,  which  contracts  it  to  a  narrow 
band  or  sliver,  and  leaves  it  coiled  up  in  a  tin  can,  ready  for 
the  next  operation.  The  process  of  carding  serves  to  equal- 
ize the  substance  of  the  cotton,  and  to  lay  its  fibres  somewhat 
in  a  more  parallel  direction. 

Drawing. — The  slivers  of  cotton  are  next  elongated  by  the 
process  of  drawing.  This  operation  is  the  ground  work  or 
principle  of  Arkwright's  invention,  and  is  used  in  the  roving 
and  spinning  as  well  as  in  the  drawing  frame.  It  is  an  imita- 
tion of  what  is  done  by  the  finger  and  thumb  in  spinning  by 
hand,  and  is  performed  by  means  of  two  pairs  of  rollers.  The 
upper  roller  of  the  first  pair,  is  covered  with  leather,  which, 
being  an  elastic  substance,  is  pressed  by  means  of  a  spring  or 
weight.  The  lower  roller,  made  of  metal,  is  fluted  in  order  to 
keep  a  firm  hold  of  the  fibres  of  cotton.  Another  similar  pair 
of  rollers  are  placed  near  those  which  have  been  described. 


ARTS  OF  COMBINING  FLEXIBLE  FIBRES. 


349 


The  second  pair,  moving  with  a  greater  velocity,  pull  out  the 
fibres  of  cotton  from  the  first  pair  of  rollers.  If  the  surface 
of  the  last  pair  move  at  twice  or  thrice  the  velocity  of  the  first 
pair,  the  cotton  will  be  drawn  twice  or  thrice  finer  than  it  was 
before.  This  relative  velocity  is  called  the  draught  of  the  ma- 
chine. This  mechanism  being  understood,  it  will  be  easy  to 
conceive  the  nature  of  the  operation  of  the  drawing  frame. 
Several  of  the  narrow  ribbands  or  slivers  from  the  cards, 
(sometimes  termed  card  ends)  by  being  passed  through  a  sys- 
tem of  rollers,  are  thereby  reduced  in  size.  By  means  of  a 
detached  single  pair  of  rollers,  the  several  reduced  ribbands 
are  plied  or  united  into  one  sliver. 

The  operations  of  drawing  and  plying  serve  to  equalize  still 
farther  the  body  of  cotton,  and  to  bring  its  fibres  more  into  a 
longitudinal  direction.  These  slivers  are  again  combined  and 
drawn  out,  so  that  one  sliver  of  the  finished  drawing  contains 
many  plies  of  card  ends.  Hitherto  the  cotton  has  acquired 
no  twist,  but  is  received  into  moveable  tin  cans  or  canisters, 
similar  to  those  used  for  receiving  the  cotton  from  the  cards. 

Roving. — The  operation  of  roving  communicates  the  first 
twist  to  the  cotton.  It  is  performed  by  a  machine  called  the 
roving  frame,  or  double  speeder.  The  tin  cans  containing  the 
slivers  of  cotton,  are  placed  upon  this  machine,  and  are  made 
to  revolve  slowly  about  their  axes  so  as  to  produce  a  slight  de- 
gree of  twisting.  The  slivers  then  pass  again  through  several 
pairs  of  rollers  moving  with  different  speeds,  and  are  thus  still 
further  attenuated  by  drawing.  They  are  then  slightly  spun 
by  the  revolution  of  flyers,  and  are  wound  upon  the  bobbins  of 
the  spindles,  in  the  form  of  a  loose,  soft,  imperfect  thread,  de- 
nominated the  roving. 

The  mechanism  of  the  double  speeder  is  complicated  and 
interesting,  and  great  ingenuity  has  been  displayed  in  overcom- 
ing the  difficulties  of  its  construction.  In  order  that  the  yarn, 
or  roving,  may  be  wound  upon  the  bobbins  in  even  cylindrical 
layers,  it  is  necessary  that  the  spindle  rail,  or  horizontal  bar 
which  supports  the  spindles,  should  continually  rise  and  fall 


350 


ARTS  OP  COMBINING  FLEXIBLE  FIBRES. 


with  a  sfow,  alternate  motion.  This  is  effected  by  heart  wheels, 
or  cams,  in  the  interior  of  the  machine.  Again,  since  the  col- 
lective size  of  the  bobbin  is  augmented  by  the  addition  of  each 
layer  of  roving,  it  is  obvious  that  if  the  axis  of  the  bobbin  re- 
volved always  with  the  same  velocity,  the  thread  of  roving 
would  be  broken  in  consequence  of  being  wound  up  too  fast. 
To  prevent  this  accident,  the  velocity  of  the  spindles,  and  like- 
wise the  motion  of  the  spindle  rail,  is  obliged  gradually  to  di- 
minish from  the  beginning  to  the  end  of  an  operation.  This 
diminution  of  speed  is  effected  by  transmitting  the  motion  both 
to  the  spindle  rail,  and  to  the  bobbins,  through  two  opposite 
cones,  one  of  which  drives  the  other  with  a  band,  the  band 
being  made  to  pass  slowly  from  one  end  to  the  other  of  the 
cones,  and  thus  continually  to  alter  their  relative  speed,  and 
cause  a  uniform  retardation  of  the  velocity  of  the  moving  parts.* 
As  the  roving  is  not  strong  enough  to  bear  any  violence,  the 
spindles  which  support  the  bobbins  are  geared  to  each  other, 
so  as  to  prevent  any  deviation  from  the  proper  velocity. 

A  more  simple  form  of  the  roving  frame,  has  been  invented, f 
in  which  the  gearing  is  dispensed  with,  as  well  as  the  pair  of 
cones  which  regulates  the  motion  of  the  bobbins.  In  this  ma- 
chine the  bobbins  are  not  turned  by  the  rotation  of  their  axis, 
but  by  friction  applied  to  their  surface  by  small  wooden  cylin- 
ders which  revolve  in  contact  with  th^m.  In  this  way  the  ve- 
locity of  the  surface  of  the  bobbin  will  always  be  the  same, 
whatever  may  be  its  growth  from  the  accumulation  of  roving, 
so  that  the  winding  goes  on  at  an  equable  rate.  To  prevent 
the  roving  from  being  stretched,  or  broken,  in  its  passage 
from  the  drawing  rollers  to  the  bobbins,  it  is  made  to  pass 
through  a  tube  which  has  a  rapid  rotation,  and  which  twists  it 
in  the  middle  into  a  cord  of  some  firmness.  It  is  again  un- 
twisted, as  fast  as  it  escapes  from  the  tube,  and  is  wound  upon 
the  bobbins  in  the  form  of  a  dense  even  cord,  but  without  any 
twist. 

*  Instead  of  band  cones,  an  ingenious  mode  of  using  geared  cones,  now  in- 
troduced in  several  American  factories,  has  already  been  described,  page  236. 
t  By  Mr  Danforth,  of  Massachusetts. 


ARTS  OF  COMBINING  FLEXIBLE  FIBRES. 


351 


Spinning. — The  bobbins  which  contain  the  cotton  in  a  state 
of  roving,  are  next  transfered  to  the  spinning  frame.  It  it  here 
once  more  drawn  out  by  rollers  and  twisted  by  flyers,  so  that 
the  spinning  is  little  more  than  a  repetition  of  the  process  gone 
through  in  making  the  roving,  except  that  the  cotton  is  now 
twisted  into  a  strong  thread,  and  cannot  any  longer  be  extend- 
ed by  drawing.  The  flyers  of  the  spinning  frame  are  driven 
by  bands,  which  receive  their  motion  in  some  cases  from  a 
horizontal  fly  wheel,  and  in  others  from  a  longitudinal  cylinder.  ^ 
As  the  thread  is  sufficiently  strong  not  to  break  with  a  slight, 
force,  the  resistance  of  the  bobbins  by  friction  is  relied  on  to 
wind  it  up,  instead  of  having  the  spindles  geared  together  and 
turned  with  an  exact  velocity,  as  they  are  in  the  common 
double  speeder.  In  the  spinning  frame  the  heart  motion  is  re- 
tained to  regulate  the  rise  and  fall  of  the  rail,  and  in  those 
frames  which  spin  the  woof,  or  filling,  it  is  applied  by  a  pro- 
gressive sort  of  cone,  the  section  of  which  is  heart  shaped, 
and  which  acts  remotely  to  distribute  the  thread  in  conical  lay- 
ers upon  the  bobbins,  that  it  may  unwind  the  more  easily  when 
placed  afterwards  in  the  shuttle. 

JWule  Spinning. — The  processes  of  water  spinning  already 
described,  are  adequate  to  produce  yarns  of  sufficient  fineness 
for  ordinary  fabrics.  But  for  producing  threads  of  the  finest 
kind,  another  process  is  necessary,  which  is  called  stretching, 
and  which  is  analogous  to  that  which  is  performed  with  carded 
cotton  upon  a  common  spinning  wheel.  In  this  operation,  por- 
tions of  yarn,  several  yards  long,  are  forcibly  stretched  in  the 
direction  of  their  length.  It  differs,  therefore,  from  the  opera- 
tion of  drawing,  in  which  a  few  inches  only  are  extended  at  a 
time.  The  stretching  is  performed  with  a  view  to  elongate 
and  reduce  those  places  in  the  yarn,  which  have  a  greater  di- 
ameter and  are  less  twisted  than  the  other  parts,  so  that  the 
size  and  twist  of  the  thread  may  become  uniform  throughout. 
To  effect  the  process  of  stretching,  the  spindles  are  mounted 

*The  latter  method  which  had  gone  into  disuse,  is  beginning  to  be  revived 
and  to  be  considered  most  advantageous. 


ARTS  OF  COMBINING  FLEXIBLE  FIBRES. 

upon  a  carriage,  which  is  moved  back  and  forwards  across  the 
floor,  receding  when  the  threads  are  to  be  stretched,  and  re- 
turning when  they  are  to  be  wound  up.  The  yarn  produced 
by  mule  spinning  is  more  perfect  than  any  other,  and  is  em- 
ployed in  the  fabrication  of  the  finest  articles.  The  sewing 
thread  spun  by  mules  is  a  combination  of  two,  four,  or  six  con- 
stituent threads,  or  plies.  Threads  have  been  produced  of 
such  fineness,  that  a  pound  of  cotton  has  been  calculated  to 
reach  167  miles. 

Warping. — The  first  step  preparatory  to  weaving  is  to  form 
a  warp,  which  consists  of  parallel  threads  continued  through 
the  whole  length  of  the  intended  piece,  and  sufiicient  in  number 
to  constitute  its  breadth.  It  was  formerly  the  practice  to  attach 
the  threads  to  as  many  pins,  and  to  draw  them  out  to  the  re- 
quired length.  But  as  this  method  required  too  much  room,  a 
warping  machine  was  subsequently  used,  in  which  the  mass  of 
threads  intended  to  constitute  a  warp,  was  wound  in  a  spiral 
course  upon  a  large  revolving  frame,  which  rose  and  fell  so 
as  to  produce  the  spiral  distribution. 

These  methods  are  now  superseded  in  this  country  by  Moody's 
warping  machine,  ^  an  ingenious  piece  of  mechanism,  in  which 
a  number  of  bobbins,  equal  to  one  eight  part  of  the  number  of 
threads  in  the  intended  warp,  are  arranged  upon  the  surface  of  a 
concave  frame.  The  threads  pass  through  a  reed  which  sepa- 
rates the  alternate  threads  as  they  are  to  be  kept  in  the  loom  ;  af- 
ter which  they  are  wound  upon  a  beam,  with  rods  interposed  at 
the  end  to  preserve  the  separation.  But  the  most  interesting 
part  of  the  mechanism  is  a  contrivance  for  stopping  the  machine 
if  a  single  thread  of  the  warp  breaks.  To  effect  this  object,  a 
small  steel  weight,  or  flattened  wire,  is  suspended  by  a  hook 
from  each  thread,  so  that  it  falls  if  the  thread  is  broken.  Be- 
neath the  row  of  weights,  a  cylinder  revolves,  furnished  with 

*  Mr  Paul  Moody,  formerly  of  Waltham,  and  now  of  Lowell,  is  the  inventor 
of  this  machine ;  likewise  of  the  spinning  frame,  which  winds  the  woof  in 
conical  layers,  and  of  great  improvements  in  the  roving  frame,  the  dressing 
frame,  &c. 


ARTS  OF  COMBINING  FLEXIBLE  FIBRES. 


353 


several  projecting  ledges  extending  its  whole  length  parallel  to 
the  axis.  When  one  of  the  weights  falls  by  the  breaking  of 
its  thread,  it  intercepts  one  of  the  ledges  and  causes  the  cylin- 
der to  exert  its  force  upon  an  elbow,  or  toggle  joint,  which  dis- 
engages R  clutch,  and  stops  the  machine.  After  the  thread  is 
tied,  and  the  weight  raised,  the  machine  proceeds. 

Dressing. — As  the  threads  which  constitute  the  warp  are 
liable  to  much  friction  in  the  process  of  weaving,  they  are 
subjected  to  an  operation  called  dressing,  the  object  of  which  is 
to  increase  their  strength  and  smoothness,  by  agglutinating  their 
fibres  together.  To  this  end  they  are  pressed  between  rollers 
impregnated  with  mucilage  made  of  starch,  or  some  gelatinous 
material,  and  immediately  afterwards  brought  in  contact  with 
brushes  which  pass  repeatedly  over  them  so  as  to  lay  down  the 
fibres  in  one  direction,  and  remove  the  superfluous  mucilage 
from  them.  They  are  then  dried  by  a  series  of  revolving  fans, 
or  by  steam  cylinders,  and  are  ready  for  the  loom. 

Weaving. — Woven  textures  derive  their  strength  from  the 
same  force  of  lateral  adhesion  which  retains  the  twisted  fibres 
of  each  thread  in  their  situations.  The  manner  in  which  these 
textures  are  formed,  is  readily  understood.  On  inspecting  a 
piece  of  plain  cloth,  it  is  found  to  consist  of  two  distinct  sits 
of  threads  running  perpendicularly  to  each  other.  Of  these, 
the  longitudinal  threads  constitute  the  warp,  while  the  transverse 
threads  are  called  the  woof,  weft,  or  filling,  and  consist  of  a 
single  thread  passing  backwards  and  forwards.  In  weaving 
with  the  common  loom,  the  warp  is  wound  upon  a  cylindrical 
beam,  or  roller.  From  this,  the  threads  pass  through  a  harness, 
composed  of  moveable  parts  called  the  heddles,  of  which  there 
are  two  or  more,  consisting  of  a  series  of  vertical  strings  con- 
nected to  frames,  and  having  loops  through  which  the  warp 
passes.  When  the  heddles  consist  of  more  than  one  set  of 
strings,  the  sets  are  called  leaves.  Each  of  these  heddles  re- 
ceives its  portion  of  the  alternate  threads  of  the  warp,  so  that 
when  they  are  moved  reciprocally  up  and  down,  the  relative 
position  of  the  alternate  threads  of  the  warp  is  reversed. 
45 


554 


ARTS  OF  COMBINING  FLEXIBLE  FIBRES. 


Each  time  that  the  warp  is  opened  by  the  separating  of  its  al- 
ternate threads,  a  shuttle  containing  tlie  woof,  is  thrown  across 
it,  and  the  thread  of  woof  is  immediately  driven  into  its  place 
by  a  frame  called  a  laij,  furnished  with  thin  reeds,  or  wires, 
placed  among  the  warp  like  the  teeth  of  a  comb.  The  woven 
piece,  as  fast  as  it  is  completed,  is  wound  up  on  a  second  beam 
opposite  to  the  first. 

Power  looms,  driven  by  water  or  steam,  although  a  late  in- 
vention, are  now  universally  introduced  into  manufactories  of 
cotton  and  woollens.  As  the  motions  of  the  loom  are  chiefly 
of  a  reciprocating  kind,  they  are  produced  in  some  looms  by 
the  agency  of  cranks,  and  in  others  by  cams  or  wipers,  acting 
upon  weights  or  springs. 

Twilling, — In  the  mode  of  plain  weaving  last  described,  it 
will  be  observed  that  every  thread  of  the  warp  crosses  at  every 
thread  of  the  woof,  and  vice  versa.  In  articles  which  are 
twilled  or  tweeled,  this  is  not  the  case  ;  for  in  this  manufacture 
only  the  third,  fourth,  fifth,  sixth,  Uc.  threads  cross  each  other 
to  form  the  texture.  In  the  coarsest  kinds  every  third  thread 
is  crossed,  but  in  finer  fabrics  the  intervals  are  less  frequent, 
and  in  some  very  fine  twilled  silks,  the  crossing  does  not  take 
pface  till  the  sixteenth  interval.    In  Fig.  1  is  shown  a  magnified 


Fig.  1. 


section  of  a  piece  of  plain  cloth,  in  which  the  woof  passes  al- 
ternately over  and  under  every  thread  of  the  warp.    In  Fig.  2, 

Fig.  2. 

is  a  piece  of  twilled  cloth,  in  which  the  thread  of  the  woof 
passes  alternately  over  four,  and  under  one,  of  the  threads  of 
the  warp,  and  performs  the  reverse  in  its  return.  To  produce 
this  effect,  a  number  of  leaves  of  heddles  are  required,  equal 
to  the  number  of  threads  contained  in  the  interval  between 
each  intersection,  inclusive.    By  the  separate  movements  of 


ARTS  OF  COMBINING  FLEXIBLE  FIBRES. 


365 


these,  the  warp  is  placed  in  the  requisite  position  before 
each  stroke  of  the  shuttle.  A  loom  invented  in  this  coun- 
try by  Mr  Batchelder,  of  Lowell,  has  been  applied  to  the 
weaving  of  twilled  goods  by  water  power. 

Twilled  fabrics  are  thicker  than  plain  ones,  when  of  the 
same  fineness,  and  more  flexible  when  of  the  same  thickness. 
They  are  also  more  susceptible  of  ornamental  variations. 
Jeans,  dimoties,  serges,  he,  are  specimens  of  this  kind  of 
texture. 

Double  Weaving. — In  this  species  of  weaving,  the  fabric  is 
composed  of  two  webs,  each  of  which  consists  of  a  separate 
warp  and  a.  separate  woof.  The  two,  however,  are  interwoven 
at  intervals,  so  as  to  produce  various  figures.  The  junction  of 
the  two  webs  is  formed  by  passing  them  at  intervals  through 
each  other,  so  that  each  particular  part  of  both  is  sometimes 
above,  and  sometimes  below.  It  follows  that  when  different 
colors  are  employed,  as  in  carpeting,  the  figure  is  the  same  on 
both  sides,  but  the  color  is  reversed.  A  section  of  double 
cloth  is  shown  in  Fig.  3. 


Fig.  3. 


The  weaving  of  double  cloths  is  commonly  performed  by  a 
complicated  machine  called  a  draw  loom,  in  which  the  weaver, 
aided  by  an  assistant,  or  by  machinery,  has  the  command  of  each 
particular  thread  by  its  number.  He  works  by  a  pattern,  in  w^iich 
the  figure  before  him  is  traced  in  squares,  agreeably  to  which  the 
threads  to  be  moved  are  selected  and  raised,  before  each  in- 
sertion of  the  woof.  Kidderminster  carpets,  and  Marseilles 
quilts,  are  specimens  of  this  mode  of  weaving. 

Cross  Weaving. — This  method  is  used  to  produce  the  Hght- 
est  fabrics,  such  as  gauze,  netting,  catgut,  he.  In  the  kinds  of 
weaving  which  have  been  previously  described,  the  threads  of 
the  warp  always  remain  parallel  to  each  other,  or  without 


350  ARTS  OF  COMBINING  FLEXIBLE  FIBRES. 

crossing.  But  in  gauze  weaving,  the  two  threads  of  warp 
which  pass  between  the  same  splits  of  the  reed,  are  crossed 
over  each  other,  and  partially  twisted  like  a  cord,  at  every 
stroke  of  the  loom.  They  are,  however,  twisted  to  the  right 
and  left,  alternately,  and  each  shot,  or  insertion  of  the  woof 
preserves  the  twist  which  the  warp  has  received.  A  great  va- 
riety of  fanciful  textures  are  produced  by  variations  of  the  same 
general  plan.  Fig.  4,  represents  the  cross  weaving  used  in 
common  gauze. 

Fig.  4. 


Lace. — Lace  is  a  complicated,  ornamental  fabric,  formed  of 
fine  threads  of  linen,  cotton,  or  silk.  It  consists  of  a  net  work 
of  small  meshes,  the  most  common  form  of  which  is  hexagonal. 
In  perfect  thread  lace,  four  sides  of  the  hexagon  consist  of 
threads  which  are  twisted,  w^hile  in  the  remaining  two,  they  are 
simply  crossed.  Lace  has  been  commonly  made  upon  a  cush- 
ion or  pillow,  by  the  slow  labor  of  artists.  A  piece  of  stiff 
parchment  is  stretched  upon  the  cushion,  having  holes  pricked 
through  it,  in  which  pins  are  inserted.  The  threads  previously 
wound  upon  small  bobbins,  are  woven  round  the  pins  and 
twisted  in  various  vvays,  by  the  hands,  so  as  to  form  the  required 
pattern.  The  expensiveness  of  the  different  kinds  of  lace  is 
proportionate  to  the  tediousness  of  the  operation.  Some  of 
the  more  simple  fabrics  are  executed  with  rapidity,  while  oth- 
ers, in  which  the  sides  of  the  meshes  are  plaited,  as  in  the 
Brussels  lace,  and  that  made  at  Valenciennes,  are  difficult,  and 
bear  a  much  greater  price. 

The  cheaper  kinds  of  lace,  have  long  been  made  by  ma- 
chinery. And  recently  the  invention  of  Mr  Heathcoats'  lace 
machine,  has  effected  the  fabrication  of  the  more  difficult  or 
twisted  lace,  with  precision  and  despatch.  This  machine  is 
exceedingly  complicated  and  ingenious,  and  is  now  in  operation 
in  this  country  and  in  France,  as  well  as  in  England. 


ARTS  OF  COMBINTNG  FLEXIBLE  FIBRES. 


357 


Carpeting. — Carpets  are  thick  textures  composed  wholly  or 
partly  of  wool,  and  wrought  by  several  dissimilar  methods. 
The  simplest  mode  is  that  used  in  weaving  the  Venetian  car- 
pets, which  is  a  plain  texture,  composed  of  a  striped  woollen 
warp,  on  a  thick  woof  of  linen  thread.  Kidderminster  carpet- 
ing is  composed  by  two  woollen  webs,  which  intersect  each 
other  in  such  a  manner  as  to  produce  definite  figures.  Brussels 
carpeting  has  a  basis  composed  of  a  warp  and  woof  of  strong 
linen  thread.  But  to  every  two  threads  of  linen  in  the  warp, 
there  is  added  a  parcel  of  about  ten  threads  of  woollen  of  dif- 
ferent colors.  The  linen  thread  never  appears  on  the  upper 
surface,  but  parts  of  the  woollen  threads  are  from  time  to  time 
drawn  up  in  loops,  so  as  to  constitute  ornamental  figures,  the 
proper  color  being  each  time  selected  from  the  parcel  to  which 
it  belongs.  A  sufficient  number  of  these  loops  is  raised  to 
produce  a  uniform  surface,  as  seen  in  Fig.  5,  and  to  render 


them  equal,  each  row  passes  over  a  wire,  which  is  subsequently 
withdrawn.  In  some  cases  the  loops  are  cut  through  with  the 
end  of  the  wire,  which  is  sharpened  for  the  purpose  so  as  to 
cut  off  the  threads  as  it  passes  out.  In  forming  the  figure,  the 
weaver  is  guided  by  a  pattern,  which  is  drawn  in  squares  upon 
a  paper.  Turkey  carpets  appear  to  be  fabricated  upon  the 
same  general  principles  as  the  Brussels,  except  that  the  texture 
is  all  woollen,  and  the  loops  larger  and  always  cut. 

Tapestry. — The  name  of  tapestry  is  given  to  certain  delicate 
and  complicated  fabrics,  in  which  the  forms  and  colors  of  natu- 
ral objects  are  produced  with  such  accuracy,  as  to  resemble 
fine  paintings.  The  mode  of  texture  used  to  produce  this  ef- 
fect, is  in  many  respects  analogous  to  that  by  which  the  finer 
carpetings  are  made.  The  minuteness,  however,  of  the  con- 
stituent parts,  causes  the  sight  of  the  texture  to  be  lost  in  the 


358 


ARTS  OF  COMBINING  FLEXIBLE  FIBRES. 


general  effect  of  the  piece.  The  fabrication  of  tapestry  is 
slow,  intricate,  and  very  expensive.  The  most  celebrated 
manufactory  is  that  established  by  the  family  of  Gobelins,  and 
kept  up  by  their  successors,  at  Paris. 

Velvets. — The  fine,  soft  knap,  by  which  velvet  is  covered, 
is  produced  by  a  method  not  unlike  that  which  is  used  in  car- 
peting, and  tapestry.  It  is  formed  of  a  part  of  the  threads  of 
the  warp,  which  the  workman  puts  in  loops  on  a  long  channel- 
led wire.  Before  the  wire  is  withdrawn,  the  row  of  loops  is 
cut  open  by  a  sharp  steel  instrument,  which  is  drawn  along  the 
channel  of  the  wire.  Various  other  fabrics  of  silk,  cotton,  and 
wool,  such  as  thicksets,  plushes,  corduroys,  velveteens,  &ic.,  are 
cut  in  a  similar  manner. 

Cotton  counterpanes  are  woven  with  two  shuttles,  one  con- 
taining a  much  coarser  woof  than  the  other.  The  coarser 
of  the  threads  is  picked  up  at  intervals,  with  an  iron  pin,  which 
is  hooked  at  the  point,  thus  forming  knobs  which  are  made  to 
constitute  regular  figures. 

In  cotton  fabrics,  the  web,  when  taken  from  the  loom,  is 
covered  with  an  irregular  knap,  or  down,  formed  by  the  pro- 
jecting ends  of  the  fibres.  This  is  removed  in  the  finest  arti- 
cles, by  burning  it  off,  the  heat  being  so  managed  as  not  to  in- 
jure the  texture  of  the  cloth.  The  operation  is  performed  by 
drawing  the  web  very  rapidly  over  an  iron  cylinder,  which  is 
kept  constantly  red  hot,  by  a  fire  within  it.  The  velocity  of 
the  cloth  prevents  it  from  burning,  while  the  loose  filaments 
which  constitute  the  knap,  are  singed  off.  The  flame  of  coal 
gas  has  of  late  been  applied  to  the  same  purpose. 

Linens. — This  name  belongs  to  fabrics  which  are  manufac- 
tured from  flax,  but  those  made  of  hemp  are  similar  in  their 
properties,  except  in  fineness.  The  length  and  comparative 
rigidity  of  the  fibres  of  flax,  present  difficulties  in  the  way  of 
spinning  it  by  the  machinery  which  is  used  for  cotton  and  wool. 
It  cannot  be  prepared  by  carding,  as  these  other  substances 
are,  and  the  rollers  are  capable  of  drawing  it  but  very  imper- 
fectly.  The  subject  of  spinning  flax  by  machinery,  has  attracted 


ARTS  OF  COMBINING  FLEXIBLE  FIBRES.  369 

much  attention,  and  the  emperor  Napoleon  at  one  time  offered 
a  reward  of  a  million  of  francs  to  the  inventor  of  the  best  ma- 
chine for  this  purpose.  Various  individuals,  both  in  this  country 
and  in  Europe,  have  succeeded  in  constructing  machines  which 
spin  coarse  threads  of  Hnen  very  well,  and  with  great  rapidity. 
But  the  manufacture  of  fine  threads,  such  as  those  used  for 
cambrics  and  lace,  continues  to  be  performed  by  hand  upon 
the  ancient  spinning  wheel. 

WOOLLENS. 

The  fibres  of  wool,  being  contorted  and  elastic,  are  drawn 
out  and  spun  by  machinery  in  some  respects  similar  to  that 
used  for  cotton,  but  differing  in  various  particulars.  Indepen- 
dently of  the  quality  of  fineness,  there  are  two  sorts  of  wool 
which  afford  the  basis  of  different  fabrics,  the  long  wool  and 
the  short.  Long  wool  is  that  in  which  the  fibres  are  rendered 
parallel  by  the  process  of  combing.  It  is  also  known  by  the 
name  oi  worsted,  and  is  the  material  of  which  camlets,  bomba- 
zines, &LC.,  are  made.  Short  wool  is  prepared  by  carding,  like 
cotton,  and  is  used,  in  different  degrees  of  fineness,  for  broad- 
cloths, flannels,  and  a  multitude  of  other  fabrics.  This  wool, 
when  carded,  is  formed  into  small  cylindrical  rolls,  which  are 
joined  together,  and  stretched  and  spun,  by  a  slubbing  or  rov- 
ing machine,  and  a  jenny  or  mule,  in  both  of  which  the  spin- 
dles are  mounted  on  a  carriage,  which  passes  backw^ards  and 
forwards,  so  as  to  stretch  the  material,  at  the  same  time  that  it 
is  twisted.  On  account  of  the  roughness  of  the  fibres,  it  is 
necessary  to  cover  them  with  oil  or  grease,  to  enable  them  to 
move  fi-eely  upon  each  other  during  the  spinning  and  weaving. 
After  the  cloth  is  w-oven,  the  oily  matter  is  removed  by  scour- 
ing, in  order  to  restore  the  roughness  to  the  fibres  preparatory 
to  the  subsequent  operation  of  fulling. 

In  articles  which  are  made  of  long  wool,  the  texture  is  com- 
plete when  the  stuff  issues  from  the  loom.  The  pieces  are 
subsequently  dyed,  and  a  gloss  is  communicated  to  them  by 


360 


ARTS  OF  COMBINING  FLEXIBLE  FIBRES. 


pressing  them  between  heated  metallic  surfaces.  But  in  cloths 
made  of  short  wool,  the  weaving  cannot  be  said  to  have  com- 
pleted the  texture.  When  the  web  is  taken  from  the  loom,  it 
is  too  loose  and  open,  and  consequently  requires  to  be  submit- 
ted to  another  operation  called  fulling.  This  is  performed  by 
a  fulling  mill,  in  which  the  cloth  is  immersed  in  water,  and 
subjected  to  repeated  compressions  by  the  action  of  large 
beaters,  formed  of  wood,  which  repeatedly  change  the  position 
of  the  cloth,  and  cause  the  fibres  to  felt  and  combine  more 
closely  together.  By  this  process  the  cloth  is  reduced  in  its 
dimensions,  and  the  beauty  and  stability  of  the  texture  are 
greatly  improved.  The  tendency  to  become  thickened  by 
fulling,  is  peculiar  to  wool  and  hair,  and  does  not  exist  in  the 
fibres  of  cotton  or  flax.  It  depends  on  a  certain  roughness  of 
these  animal  fibres,  which  permits  motion  in  one  direction, 
while  it  retards  it  in  another.  It  thus  promotes  entanglements 
of  the  fibres,  which  serve  to  shorten  and  thicken  the  woven 
fabric.  Before  the  cloth  is  sent  to  the  fulling  mill,  it  is  neces- 
sary to  cleanse  it  from  all  the  unctuous  matter,  which  was  ap- 
pHed  to  prepare  the  fibres  for  spinning. 

The  knap,  or  downy  surface  of  broadcloths,  is  raised  by  a 
process,  which,  while  it  improves  the  beauty,  tends  somewhat 
to  diminish  the  strength  of  the  texture.  It  is  produced  by 
carding  the  cloth  with  a  species  of  burrs,  the  fruit  of  the  com- 
mon teazle,  [Dipsacus  fullonum)  which  is  cultivated  for  the 
purpose.  This  operation  extricates  a  part  of  the  fibres,  and 
lays  them  in  a  parallel  direction.  The  knap,  composed  of 
these  fibres,  is  then  cut  off  to  an  even  surface,  by  the  process 
of  shearing.  This  is  performed  in  various  ways,  but  in  one  of 
the  most  common  methods  a  large  spiral  blade  revolves  rapidly 
in  contact  with  another  blade  while  the  cloth  is  stretched  over 
a  bed,  or  support,  just  near  enough  for  the  projecting  filaments 
to  be  cut  off  at  a  uniform  length,  while  the  main  texture  re- 
mains uninjured. 


ARTS  OF  COMBINING  FLEXIBLE  FIBRES. 


361 


.TING. 


The  texture  of  modern  hats,  which  are  made  of  fur  and 
wool,  depends  upon  the  process  o(  felting,  which  is  similar  to 
that  of  fulling  already  described.  The  fibres  of  these  sub- 
stances are  rough  in  one  direction  only,  a  circumstance  which 
may  be  perceived  by  passing  a  hair  through  the  fingers  in  op- 
posite directions.  This  roughness  allows  the  fibres  to  glide 
among  each  other,  so  that  when  the  mass  is  agitated,  the  ante- 
rior extremities  slide  forward  in  advance  of  the  body  or  poste- 
rior half  of  the  hair,  and  serve  to  entangle  and  contract  the 
w4iole  mass  together.  The  materials  commonly  used  for  hat 
making,  are  the  furs  of  the  beaver,  seal,  rabbit,  and  other  ani- 
mals, and  the  wool  of  sheep.  The  furs  of  most  animals  are 
mixed  with  a  longer  kind  of  thin  hair,  which  is  obliged  to  be 
first  pulled  out,  after  which  the  fur  is  cut  oft'  with  a  knife. 
The  materials  to  be  felted  are  intimately  mixed  together  by  the 
operation  of  boiving,  which  depends  on  the  vibrations  of  an 
elastic  string ;  the  rapid  alternations  of  its  motion  being  pecu- 
liarly well  adapted  to  remove  all  irregular  knots  and  adhesions 
among  the  fibres,  and  to  dispose  them  in  a  very  light  and  uni- 
form arrangement.  This  texture,  when  pressed  under  cloths 
and  leather,  readily  unites  into  a  mass  of  some  firmness.  This 
mass  is  dipped  into  a  liquor  containing  a  little  sulphuric  acid, 
and  when  intended  to  form  a  hat,  it  is  first  moulded  into  a  large 
conical  figure,  and  this  is  afterwards  reduced  in  its  dimensions 
by  working  it  for  several  hours  with  the  hands.  It  is  then 
formed  into  a  flat  surface,  with  several  concentric  folds,  which 
are  still  further  compacted  in  order  to  make  the  brim,  and  the 
circular  part  of  the  crown,  and  forced  on  a  block,  which  serves 
as  a  mould  for  the  cylindrical  part.  The  knap,  or  outer  por- 
tion of  the  fur,  is  raised  with  a  fine  wire  brush,  and  the  hat  is 
subsequently  dyed,  and  stifl^ened  on  the  inside  with  glue. 

An  attempt  has  been  made,  and  at  one  time  excited  consid- 
erable expectation  in  England,  to  form  woollen  cloths  by  the 
46 


362 


ARTS  OF  COMBINING  FLEXIBLE  FIBRES. 


process  of  felting,  without  spinning  or  weaving.  Perfect  imita- 
tions of  various  cloths  were  prodifced,  but  they  were  found  defi- 
cient in  the  firmness  and  durability  which  belongs  to  woven  fabrics. 

PAPER  MAKING. 

The  combination  of  flexible  fibres  by  which  paper  is  pro- 
duced, depends  on  the  minute  subdivision  of  the  fibres,  and 
their  subsequent  cohesion.  Linen  and  cotton  rags,  are  the 
common  material  of  which  paper  is  made,  but  hemp  and  some 
other  fibrous  substances,  are  used  for  the  coarser  kinds.  These 
materials,  after  being  washed,  are  subjected  to  the  action  of  a 
revolving  cylinder,  the  surface  of  which  is  furnished  with  a 
number  of  sharp  teeth,  or  cutters,  which  are  so  placed  as  to 
act  against  other  cutters  fixed  underneath  the  cylinder.  The 
rags  are  kept  immersed  in  water,  and  continually  exposed  to 
the  action  of  the  cutters  for  a  number  of  hours,  till  they  are 
minutely  divided,  and  reduced  to  a  thin  pulp.  During  this 
process  a  quantity  of  chloride  of  lime  is  mixed  with  the  rags, 
the  effect  of  which  is  to  bleach  them,  by  discharging  the  color- 
ing matter,  with  which  any  part  of  them  may  be  dyed,  or  oth- 
erwise impregnated.  Before  the  discovery  of  this  mode  of 
bleaching,  it  was  necessary  to  assort  the  rags,  and  select  only 
those  which  were  white,  to  constitute  white  paper.  If,  howev- 
er, the  bleaching  process  be  carried  too  far,  it  injures  the  tex- 
ture of  the  paper  by  corroding  and  weakening  the  fibres. 

The  pulp  composed  of  the  fibrous  particles  mixed  with  wa- 
ter is  transferred  to  a  large  vat,  and  is  ready  to  be  made  into 
paper.  The  workman  is  provided  with  a  mould,  which  is  a 
square  frame  with  a  fine  wire  bottom,  resembling  a  sieve,  of 
the  size  of  the  intended  sheet.  With  this  mould  he  dips  up  a 
portion  of  the  thin  pulp,  and  holds  it  in  a  horizontal  direction. 
The  water  runs  out  through  the  interstices  of  the  wires,  and 
leaves  a  coating  of  fibrous  particles,  in  the  form  of  a  sheet, 
upon  the  bottom  of  the  mould.  The  sheets  thus  formed  are 
subjected  to  pressure,  first  between  felts  or  woollen  cloths,  and 


ARTS  OF  COMBINING  FLEXIBLE  FIBRES. 


363 


afterwards  alone.  They  are  then  sized,  by  dipping  them  in  a 
thin  solution  of  gelatin,  or  glue,  obtained  from  the  shreds  and 
parings  of  animal  skins.  The  use  of  the  size  is  to  increase 
the  strength  of  the  paper,  and  by  filling  its  interstices,  to  pre- 
vent the  ink  from  spreading  among  the  fibres,  by  capillary  at- 
traction.   In  blotting  paper  the  usual  sizing  is  omitted. 

The  paper,  after  being  dried,  is  pressed,  examined,  selected, 
and  made  into  quires  and  reams.  Hot  pressed  paper  is  ren- 
dered glossy  by  pressing  it  between  hot  plates  of  polished  metal. 

Paper  is  also  manufactured  by  machinery,  and  one  of  the 
most  ingenious  methods  is  that  invented  by  the  Messrs  Four- 
drinier.  In  this  arrangement,  instead  of  moulds,  the  pulp  is 
received  in  a  continual  stream,  upon  the  surface  of  an  endless 
web,  or  brass  wire,  which  extends  round  two  revolving  cylin- 
ders, and  is  kept  in  continual  motion  forwards,  at  the  same  time 
that  it  has  a  tremulous  or  vibrating  motion.  The  pulp  is  thus 
made  to  form  a  long,  continual  sheet,  which  is  wiped  off  from 
the  wire  web,  by  a  revolving  cylinder  covered  with  flannel,  and 
after  being  compressed  between  other  cylinders  is  finally  wound 
into  a  coil,  upon  a  reel  prepared  for  the  purpose. 

Another  machine  for  making  paper  consists  of  a  horizontal 
revolving  cylinder  of  wire  w^eb,  which  is  immersed  in  the  vat 
to  the  depth  of  more  than  half  its  diameter.  The  water  pene- 
trates into  this  cylinder,  being  strained  through  the  wire  web,  at 
the  same  time  depositing  a  coat  of  fibrous  particles  on  the  out- 
side of  the  cylinder,  which  constitute  paper.  The  strained 
water  flows  ofl*  through  the  hollow  axis  of  the  cylinder,  and 
the  paper  is  wound  off  from  the  part  of  the  cylinder  which  is 
above  water,  in  the  form  of  a  continued  sheet. 


Gray's  Treatise  on  Spinning  Machinery,  8vo.  1819; — Duncan's 
Essay  on  the  Art  of  Weaving,  8vo.  1808; — Guest's  History  of  the 
Cotton  Manufacture,  4to.  1823: — Borgnis  Mechanique  Appliquee  aux 
Arts,  1818;  torn.  7,  Machines  a  Confedionner  les  Etoffes ; — Rees's 
Cyclopedia,  articles  Cotton  Manufacture,  Woollen  Manufacture, 
&c. ;— Edinburgh  Encyclopedia,  articles  Cotton  Spinning,  Cloth  Manu- 
facture, &c.  Much  of  the  machinery  invented  in  this  country,  is  not 
described  in  European  Works. 


CHAPTER  XVI. 


ARTS  OF  HOROLOGY. 

Horology,  or  the  art  of  measuring  time,  has  received  the 
attention,  and  exercised  the  ingenuity  of  mankind  from  the 
earliest  periods.  The  lapse  of  thought  and  the  routine  of  or- 
dinary occupation,  afford  but  imperfect  indications  of  the  real 
passage  of  time,  and  the  only  exact  standard  by  which  periods 
of  duration  can  be  estimated,  is  that  of  governed  and  regular 
motion. 

Sun  Dial, — The  diurnal  movement  of  the  earth  with  relation 
to  the  heavenly  bodies,  is  the  most  perfect  standard  of  admeas- 
urement for  large  periods  of  time.  It  is  the  only  one  by  which 
the  brute  creation  and  the  uncivihzed  part  of  mankind,  govern 
their  habits  of  life.  This  motion  has  been  converted  to  prac- 
tical use,  for  measuring  small  periods,  by  the  employment  of 
the  sun  dial,  an  invention  apparently  of  great  antiquity,  in 
which  the  faUing  of  a  shadow  on  a  surface  opposhe  to  the  sun, 
indicates  the  hour  of  the  day.  The  sun  dial  was  known  to 
the  ancient  Egyptians,  Chinese,  and  Bramins,  and  was  used 
by  the  latter  for  astronomical  purposes.  It  appears  also  to 
have  been  known  to  the  Jews  in  the  time  of  Ahaz,  about  740 
years  before  Christ.  The  first  sun  dial  at  Rome,  was  set  up 
by  Papirius  Cursor,  about  300  years  before  Christ,  previously 
to  which  time,  Pliny  tells  us,  there  is  no  mention  of  any  account 
of  time,  but  by  the  suns  rising  and  setting. 

At  Athens,  there  is  now  standing  an  octagonal  building  erect- 
ed by  Andronicus  Cyrrhestes,  and  commonly  called  the  Tower 
of  the  winds.  It  is  shown  in  PI.  IV.  Fig.  13.  Upon  each 
of  the  eight  sides  of  this  building,  is  a  flying  figure  carved  in 
relief,  representing  the  particular  wind  which  blew  against  that 


ARTS   OF  HOROLOGY. 


365 


side.  Upon  each  side  was  also  placed  a  vertical  sun  dial ;  the 
gnomon  or  index,  which  cast  the  shadow,  projecting  from  the 
side,  while  the  lines  indicating  the  hour,  were  cut  upon  the 
wall.  On  the  top,  according  to  Vitruvius,  was  the  figure  of  a 
Triton,  which  turned  with  the  wind  in  the  same  manner  as  a 
modern  weathercock.  The  lines  of  the  dial  upon  the  wall  are 
distinctly  extant  at  the  present  day ;  and  although  the  gnomons 
have  disappeared,  the  places  where  they  were  inserted  are  still 
visible. 

Clepsydra. — Since  the  sun  dial  could  be  used  only  in  the 
day  time,  and  in  clear  weather,  a  different  instrument  was  in- 
vented by  the  ancients,  to  be  used  within  doors,  at  all  times ; 
and  to  this  was  given  the  name  of  clepsydra.  The  clepsydra 
was  formed  by  a  vessel  of  water,  having  a  minute  perforation 
in  the  bottom,  through  which  the  water  issued  drop  by  drop. 
It  fell  into  another  vessel,  in  which  a  light  body  floated,  having 
attached  to  it  an  index  or  graduated  scale.  As  the  water  in- 
creased in  the  receiving  vessel,  the  floating  body  rose,  and  by 
its  regularly  increasing  height  furnished  an  approximation  to  the 
correct  indication  of  time.  ^ 

The  original  clepsydra  was  but  a  rude  instrument,  and  must 
have  given  imperfect  indications  of  the  true  divisions  of  time. 
When  the  vessel  was  first  filled,  the  drops  must  have  fallen 
faster,  owing  to  the  greater  height  and  pressure  of  the  fluid  ; 
and  in  proportion  as  it  became  empty,  the  dropping  would  be 
slower,  in  consequence  of  the  diminution  of  this  pressure. 
The  disadvantage,  however,  was  remedied  in  various  ways  by 
the  employment  of  two  vessels,  one  of  which  was  kept  constant- 
ly full  by  a  supply  from  the  other,  and  thus  the  water  being  al- 
ways at  the  same  height,  furnished  its  drops  under  an  equable 
pressure. 

*  This  instrument  was  invented  in  Egypt,  but  was  brought  into  Rome  from 
Athens.  Pompey,  while  consul,  introduced  it  into  the  Roman  Senate  House, 
and  the  orators  were  obliged  to  limit  the  length  of  their  speeches  by  its  divis- 
ions of  time,  so  that  Pompey  is  designated  by  one  of  the  historians,  as  the  first 
Roman  who  put  bridles  upon  eloquence. 


366 


ARTS  OF  HOROLOGV. 


W ater  Clock. — An  instrument  called  a  water  clock,  was  in 
use  at  a  much  later  date,  and  was  a  subject  of  extensive  man- 
ufacture in  some  parts  of  Europe,  a  few  centuries  ago.  Sev- 
eral modes  of  constructing  this  instrument  were  devised,  but 
the  following  is  one  of  the  most  ingenious.  A  tight  hollow  cy- 
linder, PI.  X.  Fig.  4,  is  suspended  by  cords  wound  round  its 
axis,  which  will  unwind  as  it  runs  down.  It  has  its  interior 
divided  into  several  compartments,  situated  like  the  buckets  of 
a  water  wheel.  These  compartments  communicate  with  each 
other  by  a  minute  aperture,  through  which  water  can  pass  slow- 
ly from  one  compartment  to  another.  Before  the  machine  is 
put  in  motion,  a  small  quantity  of  water  is  introduced  into  the 
lower  compartments.  As  the  cylinder  descends  by  the  unwind- 
ing of  the  cords,  it  is  obliged  to  revolve  on  its  axis,  until  the 
lower  compartments  which  contain  the  water,  have  risen  so  far 
on  the  ascending  side  as  to  produce  an  equilibrium.  It  can 
then  unwind  no  faster  than  the  water  escapes  from  one  com- 
partment to  another,  through  the  minute  apertures.  As  this 
requires  a  considerable  time,  the  cylinder  may  occupy  a  day, 
if  required,  in  descending  from  the  top  to  the  bottom  of  the 
frame  to  which  it  is  attached.  And  if  the  sides  of  the  frame 
be  marked  with  the  hours  of  the  day,  the  axis  of  the  cylinder 
as  it  passes  by  them,  will  indicate  the  time  of  the  day  with  as 
much  accuracy,  as  so  imperfect  a  machine  permits. 

Clock  Work. — In  modern  days,  all  other  methods  of  meas- 
uring time  have  given  place  to  the  equable  motion  produced 
by  the  action  of  machinery  on  the  pendulum  and  balance. 
Timekeepers  constructed  on  this  principle,  began  to  be  known  in 
Europe  about  the  14th  century,  but  were  formed  in  a  rude  and 
imperfect  manner,  until  the  middle  of  the  17th.  Since  that  period, 
the  learning  of  philosophers  and  the  ingenuity  of  artists  have 
beeti  extensively  applied  to  their  improvement,  and  few  subjects 
connected  with  the  mechanic  arts,  have  called  forth  more  in- 
ventive acuteness,  elaborate  experiment,  and  exact  calculation. 

Before  proceeding  to  a  description  of  the  entire  mechanism 
of  a  clock  or  watch,  it  will  be  useful  to  attend  to  some  of  the 


ARTS   OF  HOROLOGY. 


367 


general  principles  and  essential  parts  of  a  timekeeper.  These 
will  be  most  easily  made  intelligible  by  directing  the  attention 
to  the  following  subjects.  1.  The  maintaining  power.  2.  The 
regulating  movement.  3.  The  method  of  connexion. 

Maintaining  Power. — The  force  which  is  employed  to  sustain 
the  motions  of  timekeepers,  does  not  require  to  be  of  a  pow- 
erful kind.    It  must,  however,  be  steady  and  uniform  in  its 
action.    Gravity  and  elasticity,  applied  through  the  medium 
of  weights  and  springs,  are  the  only  means  now  employed  to 
communicate  motion  to  these  machines.    In  clocks,  the  main- 
taining force  is  usually  derived  from  a  weight.    A  weight  acts 
with  perfect  uniformity  from  the  beginning  to  the  end  of  its 
descent,  provided  the  line  which  suspends  it  is  of  equal  size 
throughout,  and  that  this  line  is  wound  upon  a  true  and  perfect 
cylinder.    In  portable  timekeepers,  the  weight,  for  obvious 
reasons,  cannot  be  employed,  and  the  spring,  although  a  less 
perfect  and  equable  power,  is  obliged  to  be  substituted.  From 
the  oldest  clocks  which  remain,  it  appears  that  the  spring  was 
in  use  before  the  weight,  and  one  of  the  first  ever  made  is  still 
preserved  at  Brussels,  in  which  the  spring  is  an  old  sword 
blade,  from  which  a  piece  of  catgut  is  wound  upon  the  cylinder' 
of  the  first  wheel.    The  principal  difficulty  in  the  use  of  the 
spring,  is,  that  its, action  is  unequal,  and  that  the  more  it  is  bent, 
the  greater  force  it  exerts  to  return  to  its  natural  situation. 
The  spring  of  a  watch,  as  it  is  now  used,  is  a  long  plate  of 
steel  coiled  up  into  a  spiral  form.    From  the  outside  of  this 
proceeds  a  chain,  which  is  attached,  not  to  a  cylinder,  as  is 
done  with  the  weight,  but  to  a  spiral  roller  called  a  fusee,  which 
by  its  conical  form,  gives  to  the  spring  an  increased  mechanical 
advantage,  in  proportion  as  its  power  diminishes.    The  fusee 
has  already  been  described,  page  337. 

In  some  of  the  watches  which  are  now  made,  the  fusee  and 
the  chain  are  dispensed  with.  The  barrel  which  incloses  the 
spring,  has  a  toothed  circle  on  its  outside,  which  turns  round  as 
the  spring  unwinds,  and  gives  motion  to  the  machinery.  But 
in  this  case  the  spring  is  made  larger  than  common,  and  only  - 


368 


ARTS   OF  HOROLOGY. 


the  middle  part  of  its  action  is  used,  it  being  never  wound  up 
so  far  as  to  call  forth  its  greatest  strength,  nor  suffered  to  run 
down  so  far  as  to  be  materially  weakened. 

Regulating  Movement. — In  the  mechanism  of  clocks  and 
watches,  it  is  necessary  so  far  to  retard  the  movement  of  the 
maintaining  force,  i.  e.  of  the  weight  or  spring,  that  it  may  be 
hours  and  days  in  expending  itself,  and  that  the  timekeeper 
may  require  to  be  wound  up  only  at  distant  and  convenient 
periods.  This  is  in  part  effected  by  the  successive  combination 
of  wheels  and  pinions,  the  last  of  which  turns  round  many 
hundred  times,  while  the  first  turns  round  once.  But  if  a  time 
keeper  possessed  only  wheels  and  pinions,  it  would  run  down 
with  a  rapidly  accelerated  motion  in  the  course  of  a  few  sec- 
onds. It  becomes,  therefore,  necessary  to  connect  with  it  an- 
other motion  which  cannot  be  accelerated  beyond  a  certain 
degree,  by  any  given  force.  This  motion  is  obtained  in  clocks 
from  the  pendulum,  and  in  watches  from  the  balance  ;  and  it  is 
the  one  which  it  was  proposed  to  consider  as  the  second  head 
under  the  name  of  the  regulating  movement. 

Pendulum. — A  pendulum  is  a  weight  capable  of  vibrating 
about  a  point  from  which  it  is  suspended.  If  the  curve  in 
which  the  pendulum  moves  be  a  circular  are,  it  is  necessary 
that  the  length  of  the  vibrations  should  be  exactly  equal ;  other- 
wise the  pendulum  will  not  keep  true  time.  But  if  the  curve 
be  a  cycloidal  one,  the  pendulum  will  move  back  and  forward 
in  equal  times,  whatever  be  the  length  of  its  vibrations.  In 
practice,  it  is  found  difficult  to  make  a  pendulum  move  in  a 
cycloidal  path  without  too  much  friction.  It  is  therefore  cus- 
tomary in  clocks  to  use  pendulums  moving  in  circular  arcs, 
these  arcs  being  made  to  approximate  to  cycloids,  by  being  as 
short  as  possible. 

Pendulums,  when  set  in  motion,  would  continue  to  vibrate 
forever,  were  it  not  for  the  retarding  effect  of  friction  and  the 
resistance  of  the  atmosphere.  The  former  of  these  is  partly 
obviated  by  hanging  the  pendulum  upon  a  thin  spring,  the  latter 
by  forming  it  with  a  sharp  edge.    Still  a  considerable  force  is 


ARTS   OF  HOROLOGY. 


369 


requisite  to  sustain  the  motion,  and  this  force  in  clocks  is  deriv- 
ed from  the  weight. 

That  pendulums  may  vibrate  in  equal  periods,  and  thus  fur- 
nish a  correct  measure  of  time,  it  is  necessary  that  they  should 
always  be  of  uniform  length,  for  pendulums  of  different  lengths 
differ  in  their  vibrations  as  the  square  roots  of  their  lengths. 
Now  such  is  the  effect  of  heat  in  expanding  all  known  sub- 
stances, particularly  metals,  that  the  same  pendulum  is  always 
longer  in  summer  than  it  is  in  winter,  and  sufficiently  so,  to  af- 
fect the  correctness  of  the  timepiece  to  which  it  is  attached. 
To  remedy  this  difficulty,  various  ingenious  contrivances  have 
been  resorted  to,  the  most  common  of  which  are  combinations 
of  metals,  so  connected  as  to  expand  in  opposite  directions, 
counterbalancing  each  other,  so  as  to  keep  the  centre  of  oscil- 
lation in  one  place.  This  is  sometimes  effected  in  the  gridiron 
pendulum,  by  combining  bars,  or  rods,  of  steel  and  brass;  and 
in  the  mercurial  pendulum,  by  inclosing  a  quantity  of  quick- 
silver in  a  tube,  near  the  bottom  of  the  pendulum. 

Balance. — As  the  pendulum  depends  upon  the  force  of  grav- 
ity for  its  motions,  it  obviously  cannot  be  employed  for  watches, 
or  portable  timekeepers,  which  are  liable  to  change  their  posi- 
tion. A  substitute  is  found  in  the  balance,  which  is  commonly 
a  wheel  moving  on  an  axis,  and  which,  when  thrown  backward 
and  forward,  by  opposite  applications  of  the  moving  force,  per- 
forms its  vibrations  in  equal  times.  The  balance  is  liable  to 
the  same  irregularities  from  expansion  and  contraction,  as  the 
pendulum,  and  is  corrected  in  a  similar  manner,  and  watches 
go  best,  when  they  are  kept  in  the  uniform  heat  of  the  body. 

The  quantity  of  matter  accumulated  in  the  balance  wheel 
of  a  common  watch,  is  so  extremely  small,  that  it  seems  im- 
possible that  it  should  exert  a  perfect  regulating  power.  The 
want  of  weight,  however,  is  in  some  measure  made  up  by 
causing  it  to  perfoi-m  large  vibrations,  and  to  move  with  great 
velocity.  The  rim  of  the  balance  wheel  in  a  good  watch, 
frequently  moves  through  ten  inches  in  every  second.  This 
velocity  is  produced  by  the  hair  spring,  which  throws  the 
47 


370 


ARTS   OF  HOROLOGY. 


balance  back  to  the  point  of  equilibrium  as  fast  as  it  is  thrown 
out  in  either  direction  by  the  moving  force,  thus  performing  for 
the  balance,  what  gravity  does  for  the  pendulum.  If  the  hair 
spring  be  taken  away,  a  watch  will  lose  more  than  12  hours  in 
24,  and  go  much  more  irregularly.  The  operation  of  the 
common  regulator  of  a  watch,  is  to  tighten  or  relax  this  hair 
spring  by  making  its  effective  part  longer  or  shorter,  thus  ac- 
celerating or  retarding  the  speed  of  the  balance. 

Scnpement, — It  remains  to  consider  the  third  part  or  scape- 
tnentj  by  which  the  rotary  motion  of  the  wheels  is  converted 
into  the  reciprocating  one  of  the  pendulum  and  balance.  In 
the  scapement,  a  certain  part  connected  with  the  pendulum 
or  balance,  is  put  in  the  way  of  the  last  or  most  rapid  wheel, 
so  that  only  one  tooth  of  this  wheel  can  escape  by  it  during 
each  vibration.  Thus  the  pendulum  or  balance,  while  it  re- 
ceives its  motion  from  this  wheel,  becomes  in  its  turn  the  regu- 
lator of  its  velocity. 

The  crutch  or  anchor  scapement,  used  in  clocks,  and  the 
common  pallet  scapement  with  a  contrate  wheel,  which  is 
the  kind  most  extensively  used  in  watches,  have  been  already 
explained  under  the  head  of  machinery,  page  245.  The 
horizontal    scapement,  Fig.  1. 

Fig.  1,  consists  of  a  wheel 
A,  with  elevated  teeth, 
the  outer  surface  of  which 
is  curved  obliquely. 
These  teeth  act  upon 
the  edges  of  a  hollow 
half  cylinder,  C,  the  axis  of  which  is  parallel  to  that  of  the 
wheel,  and  carries  the  balance  upon  one  of  its  extremities. 
When  a  tooth  of  the  scape  wheel  strikes  the  first  edge  of  the 
cylinder,  it  causes  it  to  recede,  moving  the  balance  in  one  di- 
rection. The  tooth  then  enters  the  hollow  part  of  the  cylinder 
and  strikes  upon  the  opposite  side.  Before  it  can  escape,  the 
cylinder  is  obliged  to  turn  in  the  opposite  direction,  and  thus  a 
vibrating  movement  is  kept  up  in  the  cylinder  and  balance. 


ARTS   OF  HOROLOGY. 


371 


A  multitude  of  other  scapements,  have  also  been  introduced 
bv  different  artists,  varying  from  each  other  in  the  complication 
of  their  structure,  and  accuracy  of  their  movements.  But 
these  must  necessarily  be  omitted.  The  operation  of  the  sim- 
pler forms  already  described,  will  be  more  intelligible  taken  in 
connexion  with  the  wheel  work  next  to  be  noticed. 

Bescription  of  a  Clock. — In  PI.  X,  several  views  are  given 
of  the  mechanism  of  a  clock,  consisting  of  the  going  part, 
which  moves  constantly  and  carries  the  hands  ;  and  the  striking 
part,  which  announces  the  hour.  Fig.  1,  PI.  X,  is  an  eleva- 
tion of  the  clock  with  the  wheels  seen  edgewise,  shewing  the  go- 
ing part ;  the  striking  movements  being  omitted  in  diis  figure,  to 
avoid  confusion.  Fig.  2,  is  a  front  view  of  the  wheel  ivork  of 
both  going  and  striking  parts ;  and  Fig.  3,  is  the  dial  ivork  or 
mechanism  immediately  under  the  dial,  or  face  of  the  clock, 
and  is  that  part  which  puts  the  striking  train  in  motion  every 
hour.  A  clock  of  this  kind  contains  two  independent  trains  of 
wheel  work,  each  with  its  separate  first  mover.  One  is  constant- 
ly going,  to  indicate  time  by  the  hands  on  the  dial  plate  ;  the 
other  is  put  in  motion  once  in  an  hour,  and  strikes  a  bell  to  tell  the 
hour  at  a  distance.  The  part  marked  a,  in  Figures  1  and  2,  is 
the  barrel  of  the  going  part ;  it  has  a  cargut  band,  b,  wound 
round  it,  suspending  the  weight  which  keeps  the  clock  in  motion. 
The  part  marked  96,  is  a  wheel,  called  the  first  or  great  wheel, 
of  ninetysix  teeth  upon  the  end  of  a  barrel,  turning  a  pinion 
8,  of  eight  leaves,  on  an  arbor,*  w^hich  carries  the  minute  hand  ; 
also  64,  is  a  wheel  of  64  teeth,  on  the  same  arbor,  called 
the  centre  wheel,  turning  the  wheel  60  by  a  pinion  of  eight 
leaves  on  its  arbor.  This  last  wheel  gives  motion  to  the  pinion 
of  eight,  on  the  arbor  of  the  swing  wheel  30,  w^iich  has  30  teeth. 

*  The  terms  arboVy  shaft,  axle,  and  axis,  are  synonymously  used  by  mechan- 
ics, to  express  the  bar,  or  rod,  which  passes  through  the  centre  of  a  wheel. 
The  terminations  of  a  horizontal  arbor  are  called  gudgeons,  and  of  an  upright 
one,  frequently,  pivots.  The  term  axis  in  a  more  exact  sense  may  mean 
merely  the  longest  central  diameter,  or  a  diameter  about  which  motion  takes 
place . 


I 


372 


ARTS   OF  HOROLOGY". 


The  parts  d  h,  are  the  pallets  of  the  scapement  fixed  on  an 
arhor  e,  Fig  1st,  going  through  the  back  plate  of  the  clock's 
frame,  and  carrying  a  long  lever  /.  This  lever  has  a  small 
pin  projecting  from  its  lower  end,  going  into  an  oblong  hole 
made  in  the  rod  B  of  the  pendulum. 

The  pendulum  consists  of  an  inflexible  metalhc  rod,  sus- 
pended by  a  very  slender  piece  of  steel  spring  D,  from  a  brass 
bar  E,  screwed  to  the  frame  of  the  clock,  having  a  weight  at  its 
lower  end  not  seen  in  the  figure;  in  the  present  case  inches 
from  the  suspension  D.  When  this  pendulum  is  moved  from  the 
perpendicular  line,  in  either  direction,  and  suffered  to  fall  back 
again,  it  swings  nearly  as  much  beyond  the  perpendicular  on 
the  contrary  side,  and  then  returns.  This  it  will  continue  to 
do  for  some  time,  and  each  of  these  vibrations  will  be  perform- 
ed in  one  second  of  time,  when  the  pendulum  is  of  the  above 
length.  This  is  the  measurer  of  the  time,  and  the  office  of 
the  clock  is  only  to  indicate  the  number  of  vibrations  it  has 
made,  and  to  give  it  a  small  impulse  each  time  to  keep  it  go- 
ing, as  the  resistance  of  the  air  and  elasticity  of  the  spring  D, 
would  otherwise  in  a  short  time  cause  it  to  stop.  By  the  ac- 
tion of  the  weight  applied  to  the  cord  b,  which  is  called  the 
maintaining  power,  the  wheels  are  all  turned  round  ;  and  if 
the  pallets  d  and  h,  were  removed,  the  swing  wheel  30  would 
revolve  with  great  velocity  in  the  direction  from  30  to  d,  until 
the  weight  reached  the  ground.  The  teeth  of  these  pallets  are 
so  placed,  that  one  of  them  always  engages  the  wheel  and  pre- 
vents it  from  turning  more  than  half  a  tooth  at  a  time.  In  the 
figure,  the  pallet  d,  has  the  nearest  tooth  of  the  wheel  resting 
on  it,  and  the  pendulum  is  on  the  side  h  of  the  perpendicular. 
When  it  returns,  it  moves  the  pallet  d,  so  as  to  allow  the  tooth 
of  the  wheel  to  slip  off ;  but  in  the  mean  time  the  pallet  A,  has 
interposed  its  point  in  the  way  of  the  tooth  next  it,  and  stops 
the  wheel  till  the  next  vibration  or  second.  The  distance  be- 
tween the  two  pallets  d  and  A,  is  so  adjusted,  that  only  half  a 
tooth  of  the  wheel  escapes  at  each  vibration  ;  and  as  the  wheel 
has  30  teeth,  it  will  revolve  once  in  GO  vibrations,  of  one  second 


ARTS   OF  HOROLOGY. 


373 


each,  or  in  one  minute ;  consequently  a  hand  on  the  arbor  of  this 
wheel,  will  indicate  seconds  on  the  dial  plate  F,  which  is  a  cir- 
cle divided  into  60.  The  pinion  of  eight  on  its  arbor  is  turned 
by  a  wheel  of  GO,  which  consequently  will  turn  once  in  seven 
turns  and  a  half  of  the  other,  or  in  seven  minutes  30  seconds, 
or  in  one  eighth  of  an  hour.  Its  pinion  of  eight  is  moved  by 
a  wheel  of  64,  or  eight  times  itself,  which  will  turn  in  one 
eighth  part  of  the  time.  This  will  be  an  hour,  and  therefore 
the  arbor  of  this  wheel,  carries  the  minute  hand  of  the  clock.  The 
great  wheel  of  96,  being  12  times  the  number  of  the  pinion 
eight,  will  turn  once  in  12  hours,  and  the  barrel  a  with  it.  The 
cord  of  catgut  goes  round  16  times,  so  that  the  clock  will  go 
eight  days. 

The  hour  hand  of  the  clock  is  turned  by  the  wheel  work, 
shown  in  Fig.  1,  and  3.  On  the  end  of  the  arbor  of  the  centre 
wheel  64,  a  tube  is  fitted  so  as  to  go  round  with  it  by  friction. 
This  carries  the  minute  hand,  and  if  the  clock  should  require 
correction,  the  hand  may  be  slipped  round  without  moving  the 
wheels.  This  tube  has  a  pinion  of  40  teeth  on  its  lower  end, 
indicated  by  a  dotted  circle.  This  turns  another  w^heel  40,  of 
40  teeth,  which  has  a  pinion  of  six  teeth  on  its  arbor,  turning 
a  wheel  72,  of  72  teeth.  The  tw^o  wheels  40,  will  both  turn 
in  an  hour ;  and  72,  in  12  hours.  The  arbor  of  this  wheel 
has  the  hour  hand,  and  is  a  tube  going  over  the  arbor  of  the 
minute  hand,  so  that  the  two  hands  are  concentric.  The  bar- 
rel a,  is  fitted  to  an  arbor  coming  through  the  plate  of  the  clock, 
and  filed  square  to  put  on  a  key  to  wind  up  the  weight. 
The  great  wheel  96,  is  not  fixed  fast  to  the  arbor,  but  has  a 
click  on  it,  which  takes  the  teeth  of  a  ratchet  wheel  cut  on  the 
barrel ;  so  that  the  barrel  may  be  turned  in  one  direction  to 
wind  up  the  weight,  without  the  wheel ;  but  by  the  descent  of 
the  weight,  the  wheels  will  be  turned  with  the  barrel  by  the  click. 

Striking  Part. — Having  now  considered  the  going  part  of 
the  clock,  it  remains  to  describe  the  mechanism  by  which  the 
hour  is  struck.  In  Fig.  2,  78  is  a  great  wheel  of  78  teeth, 
provided  with  a  barrel  and  click  as  in  96  ;  it  turns  a  pinion  of 


374 


ARTS   OF  IIOKOLOGY. 


eight.  On  the  same  arbor  is  a  wheel  64,  turning  a  pinion  of 
eight,  on  the  arbor  of  the  wheel  o,  of  48.  This  turns  another 
pinion  of  eight,  and  wheel  jo,  of  48,  which  turns  a  pinion  of 
six,  on  the  same  arbor  with  a  thin  vane  of  metal,  seen  edgewise, 
which  is  called  the  fly,  and  which,  by  the  resistance  of  the  air 
to  its  motion,  regulates  the  velocity  of  the  wheels. 

The  wheel  64  has  eight  pins  projecting  from  it  which  raise 
the  tail  n  of  the  hammer,  as  they  revolve.  The  hammer  is  re- 
turned violently  when  the  pins  leave  its  tail,  by  a  spring  m, 
pressing  on  the  end  of  a  pin  put  through  its  arbor ;  and  strikes 
the  bell.  The  hammer  and  bell  are  behind  the  plate,  and 
therefore  unseen.  There  is  a  short  spring  Z,  which  the  other 
end  of  the  pin  through  the  arbor  touches,  just  before  the  ham- 
mer strikes  the  bell.  Its  use  is  to  lift  the  hammer  off  the  bell, 
the  instant  it  has  struck,  that  it  may  not  stop  the  sound.  The 
pins  in  the  wheel  64,  must  pass  by  the  hammer  tail  78 
times  in  striking  the  twelve  hours,  1 4-2 +  34-4-4- 5 -j- 64-7-|-8-|- 
94. 104-11 412 1=78,  and  as  its  pinion  has  eight  leaves,  each 
leaf  of  the  pinion  answers  to  a  pin  in  the  wheel  64.  Now  as 
the  great  wheel  has  78  teeth,  it  will  turn  once  in  12  hours,  the 
same  as  the  other  great  wheel  96.  In  the  wheel  64,  eight  of 
its  teeth  correspond  to  one  of  the  pins  of  the  hammer,  and  as 
the  pinion  of  the  wheel  0,  has  eight  teeth,  it  (wheel  0)  wiW  turn 
once  for  each  stroke  of  the  hammer.  By  the  remaining 
wheels,  one,  0,  multiplying  six  times,  and  the  other,  eight 
times,  the  fly  will  turn  6  x  8  z=  48  times  for  one  turn  of  0, 
which  answers  to  one  stroke  of  the  hammer. 

Fig.  3,  is  also  mechanism  relating  to  the  striking  part.  Behind 
r  there  is  a  small  pinion  of  one  tooth,  called  the  gathering  pal- 
let ^on  the  arbor  of  the  wheel  0,  which  consequently  turns  once  for 
each  stroke  of  the  hammer.  The  part  marked  S  r  x  is  a  por- 
tion of  a  large  wheel,  and  is  called  the  7'ack.  The  part  t 
is  an  arm  attached  to  the  rack,  whose  end  rests  against  a  spiral 
plate,  V,  called  the  snail,  which  is  fixed  on  the  tubular  arbor 
before  described,  of  the  hour  hand  and  wheel  72,  and  turils 
round  widi  it  once  in  12  hours.    The  snail  is  divided  into  12 


ARTS   OF  HOROI.OCJY. 


375 


equal  angles,  of  30  degrees  each,  and  as  it  turns,  each  of  these 
answers  to  an  hour.    The  circular  arcs,  forming  the  circum- 
ference of  the  snail,  are  struck  from  the  centre  of  the  arhor 
between  each  division,  with  a  different  radius,  decreasing  a  cer- 
tain quantity  each  time  in  the  order  of  the  hours.    The  circu- 
lar part  of  the  rack,  14,  is  cut  into  teeth,  each  of  which  is  of  such 
a  length,  that  every  step  upon  the  snail  shall  answer  to  one  of 
them.    At      is  a  spring  pressing  against  the  tail  of  the  rack, 
and  acting  to  throw  the  arm  of  the  rack  against  the  snail.  The 
part     is  a  click  called  the  hawk's  bill,  taking  into  the  teeth  of 
the  rack,  and  holding  it  up  in  opposition  to  the  spring  w.  The 
part  ik\s?i  three-armed  detent,  called  the  warning  piece.  The 
arm  k  is  bent  at  its  end,  and  passes  through  a  hole  in  the  front 
plate  of  the  clock,  so  as  to  catch  a  pin  placed  in  one  of  the 
arms  of  the  wheel  p.  Fig.  2,  and  which  describes  the  dotted 
circle  in  Fig.  3.    The  other  arm  z,  stands  so  as  to  fall  in  the 
way  of  a  pin  In  the  wheel  40.    In  the  present  position  of  the 
figure,  the  wheels  of  the  striking  train  are  in  motion,  and 
would  continue  turning  until  the  gathering  pallet  at  r,  which  turns 
once  at  each  stroke  of  the  hammer,  by  its  tooth  lifts  the  rack 
5,  in  opposition  to  the  spring  w,  one  tooth  each  turn  ;  and  the 
hawk's  bill  ^  retains  the  rack',  until  a  pin  in  the  end  of  the  rack 
is  brought  in  the  way  of  the  lever  of  the  gathering  pallet  r,  and 
stops  the  wheels  from  turning  any  farther.    It  is  in  this  position 
with  the  rack  wound  up,  till  its  pin  arrests  the  tail  r,  that  we 
shall  begin  to  describe  the  operation  of  the  striking  of  the 
clock. 

The  wheel  40,  as  has  been  said  before,  turns  once  in  an 
hour,  and  consequently  at  the  expiration  of  every  hour,  the 
pin  in  it  takes  the  end  i,  and  moves  it  towards  the  spring  near 
it.  This  depresses  the  end  A;,  until  it  falls  in  the  circle  of  the 
motion  of  the  pin  in  the  wheel  Fig.  2.  At  the  same  time 
the  short  tail  depresses  one  end  of  the  hawk's  bill,  and  raises 
the  other  g,  so  as  to  clear  the  teeth  of  the  rack  s.  Immedi- 
ately the  spring  ly,  throws  the  rack  back,  until  the  end  of  its 
tail  ^,  touches  that  part  of  the  snail  which  is  nearest  it.  When 


376 


ARTS   OP  HOIIOLOGV. 


the  rack  falls  back,  the  pin  in  it  is  moved  clear  of  the  gather- 
ing pallet  r,  and  the  wheels  set  at  liberty.  The  maintaining 
power  puts  them  in  motion ;  but  in  a  very  short  time  before 
the  hammer  has  struck,  the  pin  in  the  wheel  p  falls  against  the 
end  of  /c,  and  stops  the  whole.  This  operation  happens  a  few 
minutes  before  the  clock  strikes,  and  this  noise  of  the  wheels 
turning,  is  called  the  w^arning.  When  the  hour  is  expired,  the 
wheel  40  has  turned  so  far,  as  to  allow  the  end  of  i  to  slip 
over  its  pin,  as  in  the  figure.  The  small  spring  pressing 
against  it  raises  the  end  A:,  so  as  to  be  within  the  circle  of  the 
pin  in  the  wheel  Fig.  2.  Every  obstacle  is  now  removed, 
and  the  wheels  run  on  the  pinion  ;  the  wheel  64  raises  the 
hammer  r,  and  it  strikes  on  the  bell ;  the  gathering  pallet  r, 
takes  up  the  rack,  one  tooth  at  each  turn,  the  hawk's  bill 
retaining  it  until  the  pin  x  in  the  rack  comes  under  the  gathering 
pallet  r,  and  stops  the  motion  of  the  whole  machine,  till  the  pin 
in  the  wheel  40  at  the  next  hour  takes  the  warning  piece  ik^ 
and  repeats  the  operation  we  have  now  described.  As  the 
gathering  pallet  turns  once  for  each  blow  of  the  hammer,  and 
its  tooth  gathers  up  one  tooth  of  the  rack  at  each  turn,  it  is  evi- 
dent, that  the  number  of  teeth  which  the  rack  is  allowed  to  fall 
back,  limits  the  number  of  strokes  the  hammer  will  make. 
This  is  done  by  the  rack's  tail  resting  on  the  snail.  Each 
step  of  the  snail  answers  to  one  tooth  of  the  rack,  and  one 
stroke  of  the  hammer.  At  each  hour,  a  fresh  step  of  the 
snail  is  turned  to  the  tail  of  the  rack,  and  by  this  means  the 
number  of  strokes  is  made  to  increase  one  at  each  time  from 
1  to  12. 

Description  of  a  Watch. — In  PI.  XI.  several  views  are  giv- 
en of  the  construction  of  a  common  })ortable  watch.  Fig.  1 
represents  the  wheel  work  immediately  beneath  the  dial  plate, 
and  also  its  hands,  the  circles  of  hours  and  minutes  being 
marked,  though  the  dial  on  which  these  are  engraved  is  re- 
moved. Fig.  2  is  a  plan  of  the  wheel  work  all  exhibited  at 
one  view,  for  which  purpose  the  upper  plate  of  the  watch  is 
removed.    Fig.  3  is  a  plan  of  the  balance,  and  the  work 


ARTS   OF   HOROLOGY.  ^7  / 

situated  upon  the  upper  plate.  Fig.  4  shows  the  great  wheel 
and  the  pottance  wheel  detached.  Fig.  5  the  spring  barrel, 
chain,  and  fusee  detached  ;  and  Fig.  6  is  an  elevation  of  all 
the  movements  together,  the  works  being  supposed  to  be  open- 
ed out  into  a  straight  line,  to  exhibit  them  all  at  once.  Fig.  7 
is  a  detached  view  of  the  balance,  together  with  the  scapement, 
in  action. 

The  principal  frame  for  supporting  the  acting  parts  of  the 
watch,  consists  of  two  circular  plates,  marked  C  and  D  in  the 
figures.  Of  these  the  former  is  called  the  upper  plate,  and  the 
latter  the  pillar  plate,  from  the  circumstance  that  the  four  pil- 
lars, E  E,  which  unite  the  two  plates  and  keep  them  a  prop- 
er distance  asunder,  are  fastened  firmly  into  the  lower  plate ; 
while  the  other  ends  pass  through  holes  in  the  upper  plate,  C, 
and  have  small  pins  put  through  the  ends  of  the  pillars,  to  keep 
the  whole  together.  By  drawing  out  these  pins,  the  watch 
may  be  taken  to  pieces.  The  pivots  of  the  several  wheels  being 
received  in  small  holes  made  in  these  plates,  they  of  course 
fall  to  pieces  as  soon  as  the  plates  are  separated. 

The  maintaining  power  is  a  spiral  steel  spring,  w^hich  is  coil- 
ed up  close  by  a  tool  used  for  the  purpose,  and  put  into  a  brass 
box  called  the  barrel.  It  is  marked  A  in  all  the  figures,  and  is 
shown  separate  in  Fig.  5,  with  the  spring  in  it.  The  spring  has 
a  hook  at  the  outer  end  of  its  spiral,  which  is  put  through  a 
hole,  a.  Fig.  5,  in  the  side  of  the  barrel,  and  rivetted  fast 
to  it.  The  inner  end  of  the  spiral  has  an  oblong  opening  cut 
through  it,  to  receive  a  hook  upon  the  barrel  arbor,  B,  Fig.  5. 
The  pivots  of  this  arbor  pass  through  the  top  and  bottom  of  the 
barrel,  and  one  of  them  is  filed  square  to  hold  a  ratchet  wheel, 
6,  Figs  1  and  6,  which  has  a  click  and  keeps  the  arbor  from 
turning  round,  except  in  one  direction.  The  two  pivots  of  the 
arbor  are  received  in  pivot  holes  in  the  plates  C  D  of  the 
watch,  and  the  pivot  which  has  the  ratchet  wheel  upon  it,  pas- 
ses through  the  plate.  The  wheel  marked  6,  Figs.  1  and  6, 
with  its  click,  is  therefore  on  the  outside  of  the  pillar  plate  D 
of  the  watch.  The  top  of  the  barrel  has  a  cover  or  lid  fitted 
48 


378 


ARTS  OF  HOROLOGY. 


into  it,  through  which  the  upper  pivot  of  the  arbor  projects ; 
thus  the  arbor  of  the  barrel  is  to  be  considered  as  a  fixture, 
the  click  of  the  ratchet  wheel  preventing  it  from  turning  round, 
while  the  interior  end  of  the  spiral  spring  being  hooked,  assists 
in  rendering  it  stationary.  The  barrel  thus  mounted  has  a 
small  steel  chain,  Figs.  2  and  6,  coiled  round  its  circumfer- 
ence, and  attached  to  it  by  a  small  hook  of  the  chain  which 
enters  a  little  hole,  made  in  the  circumference  of  the  barrel  at  its 
upper  end.  The  other  extremity  of  this  chain  is  hooked  to 
the  lower  part  of  the  fusee,  marked  F,  Figs.  2,  5,  and  6,  and 
the  chain  is  disposed  either  upon  the  circumference  of  the  bar- 
rel, or  in  the  spiral  groove  cut  round  the  fusee  for  its  reception, 
the  arbor  of  which  has  pivots  at  the  ends,  which  are  received 
into  pivot  holes  made  in  the  plates  of  the  watch.  One  pivot 
is  formed  square  and  projects  through  the  plate,  to  fit  the 
key  by  which  the  watch  is  wound  up. 

It  is  evident  that  when  the  fusee  is  turned  by  the  watch-key, 
it  will  wind  the  chain  off  the  circumference  of  the  barrel  on 
itself;  and  as  the  outer  end  of  the  spring  is  fastened  to  the 
barrel,  and  the  other  is  hooked  to  the  barrel  arbor,  which  as 
before  mentioned,  is  prevented  from  turning  by  the  click  of 
the  ratchet  wheel,  ah ;  the  spring  will  be  coiled  up  into  a 
smaller  compass  than  before.  Its  reaction,  therefore,  when 
the  key  is  taken  off,  will  turn  the  barrel,  and  by  the  chain, 
turn  the  fusee  tmd  give  motion  to  the  wheels  of  the  watch. 
The  fusee  has  a  spiral  groove  cut  round  it,  in  which  the  chain 
lies ;  this  groove  is  cut  by  an  engine,  in  such  a  form  that  the 
chain  shall  pull  from  the  smallest  part,  or  radius,  of  the  fusee, 
when  the  spring  is  quite  wound  up,  and  therefore  acts  with  its 
greatest  force  on  the  chain.  From  this  point  the  groove  grad- 
ually increases  in  diameter,  so  that  as  the  spring  unwinds  and  acts 
with  less  power,  the  chain  operates  on  a  larger  radius  of  the 
fusee ;  and  the  effect  upon  the  arbor  of  the  fusee,  or  the  toothed 
wheel  attached  to  it,  will  always  be  equal,  and  cause  the  watch 
to  go  with  regularity. 


ARTS  OF  HOROLOGY. 


379 


To  prevent  too  much  chain  being  wound  upon  the  fusee, 
and  by  that  means  breaking  the  chain  or  overstraining  the 
spring,  a  contrivance  called  a  guard-gut  is  added.  It  is  a  small 
lever,  e,  Fig.  2,  moving  on  a  stud  fixed  to  the  upper  plate  C 
of  the  watch,  and  pressed  downwards  by  a  small  spring,/.  As 
the  chain  is  wound  upon  the  fusee,  it  rises  in  the  spiral  groove, 
and  lifts  up  the  lever  until  it  touches  the  upper  plate.  It  is 
then  in  a  position  to  intercept  the  edge  or  tooth,  g,  of  the  spi- 
ral piece  of  metal  seen  on  the  top  of  the  fusee,  and  thus  stops 
it  from  being  wound  up  any  further. 

The  power  of  the  spring  is  transmitted  to  the  balance  by 
means  of  several  toothed  wheels,  which  multiply  the  number  of 
revolutions  which  the  chain  makes  on  the  fusee,  to  such  a  number, 
that  though  the  last  or  balance  wheel  turns  91  times  every 
minute,  the  fusee  will  at  the  same  time  turn  so  slowly,  that  the 
chain  will  not  be  drawn  off  from  it  in  less  than  28  or  30  hours, 
and  it  will  make  only  one  turn  in  four  hours.  This  assemblage 
of  wheels  is  called  the  train  of  the  watch.  The  first  toothed 
wheel,  G,  is  attached  to  the  fusee,  and  is  called  the  great  wheel. 
It  is  shown  separated  from  the  fusee,  in  Fig.  4,  having  a  hole 
through  the  centre  to  receive  the  arbor  of  the  fusee,  and  a 
projecting  ring  upon  its  surface.  The  under  surface  of  the 
base  of  the  fusee  is  shown  in  Fig.  5,  at  F,  having  a  circular 
cavity  cut  in  it  to  receive  the  corresponding  ring  upon  the 
great  wheel  G,  Fig.  4.  A  ratchet  wheel,  i,  is  fixed  fast  upon 
the  fusee  arbor,  and  sunk  within  the  cavity  excavated  in  the 
lower  surface  of  the  fusee.  When  the  wheel  and  fusee  are 
put  together,  a  small  click,  h,  Fig.  4,  takes  into  the  teeth  of  the 
rachet  i.  As  the  fusee  is  turned  by  the  watch-key  to  wind  up 
the  watch,  this  click  slips  over  the  sloping  slides  of  the  teeth 
without  turning  the  great  wheel ;  but  when  the  fusee  is  turned 
the  other  way  by  drawing  the  chain  from  the  spring  barrel,  the 
chck  catches  the  teeth  of  the  ratchet  wheel,  and  causes  the 
toothed  wheel  to  turn  with  the  fusee. 

The  great  wheel,  G,  has  48  teeth  on  its  circumference, 
which  take  into  and  turn  a  pinion  of  12  teeth,  fixed  on  the 
same  arbor  with  the 


380 


ARTS  OF  HOROLOGY. 


Centre  wheel,  H,  so  called  from  its  situation  in  the  centre  of 
the  watch ;  it  has  54  teeth  to  turn  a  pinion  of  six  leaves,  on 
the  arbor  of  the 

Third  wheel,  I,  which  has  48  teeth.  It  is  sunk  in  a  cavity 
formed  in  the  pillar  plate,  and  turns  a  pinion  of  six,  on  the  ar- 
bor of  the 

Contrate  wheel,  K,  which  has  48  teeth  cut  parallel  with  its 
axis,  by  which  it  turns  a  pinion  of  six  leaves,  fixed  to 

The  balance  ivheel,  L.  One  of  the  pivots  of  the  arbor  of  this 
wheel  turns  in  a  frame,  M,  called  the  pottance,  or  potence,  fixed  to 
the  upper  plate,  and  shown  separately  in  Fig.  4.  The  other  pivot 
runs  in  a  small  piece  fixed  to  the  upper  part,  called  the  counter 
pottance,  not  shown  in  any  of  the  figures ;  so  that  when  the 
two  plates  are  put  together,  the  balance  wheel  pinion  may  work 
into  the  teeth  of  the  contrate  wheel,  as  shown  in  Fig.  6.  The 
balance  wheel,  L,  has  15  teeth,  by  which  it  impels  the  balance 
op.  The  arbor  of  the  balance,  which  is  called  the  verge, 
has  two  small  leaves  or  pallets  projecting  from  it,  nearly  at  right 
angles  to  each  other.  These  are  acted  upon  by  the  teeth  of  the 
balance  wheel,  L,  in  such  a  manner,  that  at  every  vibration  the 
balance  receives  a  slight  impulse  to  continue  its  motion,  and 
every  vibration  so  made,  suffers  a  tooth  of  the  wheel  to  escape 
or  pass  by,  whence  this  part  is  called  the  scapement  of  the 
watch,  and  constitutes  its  most  essential  part.  The  wheel  L, 
is  sometimes  called  the  scape  wheel,  or  crown  wheel.  Its  ac- 
tion is  explained  by  Fig.  7,  which  shows  the  wheel  and  bal- 
ance detached.  Suppose  in  this  view,  the  pinion  h,  on  the 
arbor  of  the  balance  wheel  or  crown  wheel,  i  k,  to  be  actuated 
by  the  main  spring  which  forms  the  maintaining  power,  by 
means  of  the  train  of  wheel-work,  in  the  direction  of  the  arrow, 
while  the  pallets  m  and  n,  attached  to  the  axis  of  the  balance, 
and  standing  at  right  angles  to  each  other,  or  very  nearly  so, 
are  long  enough  to  fall  in  the  way  of  the  ends  of  the  sloped 
teeth  of  the  wheel  when  turned  round  at  an  angle  of  45  de- 
grees, so  as  to  point  to  opposite  directions,  as  in  the  figure. 
Then  a  tooth  in  the  wheel  below  for  instance,  meets  with  the 


ARTS   OF  HOROLOGY. 


381 


pallet  n,  supposed  to  be  at  rest,  and  drives  it  before  it  a  cer- 
tain space,  till  the  end  of  the  tooth  escapes.  In  the  mean  time 
the  balance,  ospr,  attached  to  the  axis  of  the  pallets,  contin- 
ues to  move  in  the  direction  r  o  sp,  and  winds  up  the  small 
spiral,  or  hair  spiing,  one  end  of  which  is  fast  to  the 
axis,  and  the  other  to  a  stud  on  the  upper  plate  of  the  frame. 
In  this  operation,  the  spring  opposes  the  momentum  given  to 
the  balance  by  this  push  of  the  tooth  upon  the  pallet,  and  pre- 
vents the  balance  going  quite  round  ;  but  the  instant  the  tooth 
escapes,  the  upper  pallet,  m,  meets  with  another  tooth  at  the 
opposite  side  of  the  wheel's  diameter,  moving  in  an  opposite 
direction  to  that  below.  Here  this  pallet  receives  a  push  which 
carries  the  balance  back  again,  its  momentum  as  yet  be- 
ing small  in  the  direction  ospr,  and  aids  the  spring, 
which  now  unbends  itself  till  it  comes  to  its  quiescent  position, 
then  swings  beyond  that  point,  partly  by  the  impulse  from  the 
maintaining  power  on  the  pallet  m,  and  partly  by  the  acquired 
momentum  of  the  moving  balance,  particularly  when  this  pallet 
m,  has  escaped.  At  length  the  pallet  n  again  meets  with  the 
succeeding  tooth,  and  is  carried  backward  by  it  in  the  direction 
in  which  the  balance  is  now  moving,  till  the  maintaining  power 
and  force  of  the  unwound  spring  together  overcome  the  mo- 
mentum of  the  balance,  during  which  time  the  recoil  of  the 
balance  wheel  is  apparent,  and  also  of  the  seconds  hand,  if  the 
watch  has  one,  its  place  being  on  the  arbor  of  the  contrate  wheel. 
Then  the  wheel  brings  the  pallet  n  back  again  till  it  escapes, 
and  the  same  process  takes  place  with  the  pallet  m  as  has  been 
described  with  respect  to  pallet  n.  Thus  two  contrary  excur- 
sions or  oscillations  of  the  balance  take  place  before  one  tooth 
has  completely  escaped,  and  for  this  reason  there  must  always 
be  an  odd  number  of  teeth  in  this  wheel,  that  a  space  on  one 
side  of  the  wheel  may  always  be  opposite  to  a  tooth  on  the 
other,  in  order  that  one  pallet  may  be  out  of  action  while  the 
other  is  in  action. 

The  upper  pivot  of  the  verge  is  supported  in  a  cover  screwed 
to  the  upper  plate,  as  shown  at  N,  in  Fig.  6,  which  extends  over 


f 


382  ARTS  OF  HOROLOGY. 

the  balance  and  protects  it  from  violence.  The  lower  pivot 
works  in  the  bottom  of  the  pottance,  M.  at  Fig.  4.  The 
socket  for  the  pivot  of  the  balance  wheel,  is  made  in  a  small 
piece  of  brass,  which  slides  in  a  groove  made  in  the  pottance, 
as  shown  Fig.  4,  so  that  by  drawing  the  slide  in  or  out,  the 
teeth  of  the  balance  wheel  shall  just  clear  one  pallet  before  it 
takes  the  other ;  and  upon  the  perfection  of  this  adjustment, 
which  is  called  the  scaping  of  the  watch,  the  performance  of  it 
very  greatly  depends. 

It  now  remains  to  show  the  communication  of  this  motion  to  the 
hands  of  the  watch,  which  indicate  the  time  on  the  dial  plate. 
The  hands  are  moved  by  the  central  arbor,  which  comes 
through  the  pillar  plate  and  projects  a  considerable  length.  It 
has  a  pinion  of  12  leaves,  called 

The  common  pinion,  w,  Fig.  6,  fitted  upon  it,  the  axis  of 
which  is  a  tube  formed  square  at  the  end,  to  fix  on  the  minute 
hand,  W.  It  fits  tight  upon  the  projecting  arbor  of  the  centre 
wheel,  and  therefore  turns  with  it,  but  will  slip  round  to  set  the 
hands  when  the  watch  is  wrong  and  requires  to  be  rectified. 
The  common  pinion  is  situated  close  to  the  pillar  plate,  and  its 
leaves  engage  the  teeth  of 

The  minute  wheel,  X,  Figs.  1  and  6,  of  48  teeth,  which  is 
fitted  on  a  pin  fixed  in  the  plate,  and  its  pinion,  a?,  of  16  leaves, 
which  is  fixed  to  it,  turns 

The  hour  wheel,  Y,  of  48  teeth.  The  arbor  of  this  is  a 
tube,  which  is  put  over  the  tube  of  the  cannon  pinion  carrying 
the  minute  hand,  and  has  the  hour  hand,  Z,  fixed  on  it,  to  indi- 
cate the  time  upon  the  dial  plate.  Thus,  by  the  cannon  pinion, 
w,  which  is  to  the  minute  wheel,  X,  as  one  is  to  four,  and  the 
pinion  x  of  this,  which  is  to  the  hour  wheel,  Y,  as  one  is  to 
three,  the  hour  wheel  Y,  and  its  hand  z,  though  concentric 
with  the  cannon  pinion  and  minute  hand,  make  but  one  revolu- 
tion during  12  revolutions  of  the  other ;  therefore  one  turns 
round  in  an  hour,  and  the  other  turns  round  once  in  12  hours, 
as  the  figures  on  the  dial  show. 


ARTS   OF  HOROLOGY. 


383 


It  is  necessary  to  have  some  regulation  by  which  the  rate  of 
the  watch's  movement  may  be  adjusted,  for  hitherto  we  have 
only  spoken  of  making  the  watch  keep  ahvays  to  a  uniform,  or 
certain  rate  of  motion,  but  it  is  necessary  to  make  it  keep  true 
time.  This  can  be  done  by  two  means,  either  by  increasing 
or  diminishing  the  force  of  the  main  spring,  which  increases  or 
diminishes  the  arc  which  the  balance  describes  ;  or  it  may  be 
done  by  strengthening  or  weakening  the  hair  spring,  which 
will  cause  the  balance  to  move  quicker  or  slower. 

The  hair  spring,  otherwise  called  the  pendulum  spring,  q, 
Fig.  3,  is  fixed  to  a  stud,  upon  the  plate  c,  by  one  end,  and  is 
attached  to  the  verge  of  the  balance  by  the  other. 

The  regulation  is  effected  by  means  of  what  is  called  the 
curb.  This  is  a  small  lever,  z,  Fig.  3,  projecting  from  a  circu- 
lar ring,  r  r,  which  may  be  considered  as  its  centre  of  motion, 
but  perforated  with  a  hole  through  the  centre,  large  enough  to 
contain  the  hair  spring  within  it.  A  circular  groove  is 
turned  out  in  the  upper  plate,  nearly  concentric  with  the  bal- 
ance, and  the  ring,  r  r,  fits  into  this.  Both  are  turned  rather 
largest  at  the  bottom,  in  the  manner  of  a  dove-tail ;  but  the 
ring  being  divided  at  the  side  opposite  to  the  lever,  z,  can  be 
sprung  up  and  rendered  so  much  smaller  as  to  get  it  into  the 
groove,  and,  being  once  in,  the  elasticity  of  the  ring  expands 
it,  so  as  to  fill  the  groove  completely.  In  this  state  it  may  be 
considered  as  a  lever  which  describes  a  circuit  round  the  verge 
as  a  centre,  and  the  end  of  it  points  to  a  divided  arc  engraved 
on  the  upper  plate,  one  end  of  which  is  marked  F,  and 
the  other  S,  denoting  that  the  index  or  lever,  z,  is  to  be  moved 
towards  one  or  the  other,  to  make  the  watch  move  faster  or 
slower  as  its  regulation  requires. 

The  manner  of  its  operation  is  thus ;  the  end  of  the  lever, 
or  index,  z,  continues  within  the  circle  a  small  distance  towards 
its  centre,  and  passing  beneath  the  outer  turn  of  the  spiral 
spring  q,  has  two  very  small  pins  rising  up  from  it,  which  in- 
clude the  spring  between  them.  The  actual  length  of  the  hair 
spring  is  therefore  to  be  estimated  from  these  pins  to  the  place  of 


384 


ARTS  OF  HOROLOGY. 


its  connexion  with  the  verge.  Now  by  altering  the  position 
of  the  index,  this  acting  length  can  be  regulated  at  pleasure,  to 
produce  such  vibration  of  the  balance  as  will  make  the  watch 
keep  true  time.  By  shortening  the  length,  the  spring  becomes 
more  powerful,  and  returns  the  balance  quicker,  so  that  it  will 
vibrate  in  less  time.  This  is  effected  by  moving  the  index  to- 
wards F.  On  the  other  hand,  turning  the  index  toward  S, 
lengthens  the  spring  by  which  it  becomes  more  delicate,  and 
less  powerful,  returning  the  balance  slower  than  before. 

Many  watches,  instead  of  the  arc  and  index,  have  a  circular 
curb,  or  regulator,  which  is  turned  by  a  central  arbor,  to  which 
the  watch-key  is  applied,  when  it  is  necessary  to  move  it. 

Delicate  watches  have  jewelled  pivot  holes  for  the  top  and 
bottom  of  the  verge,  to  diminish  the  friction.  These  jewels 
are  diamonds,  rubies,  and  other  stones,  which  unite  great  hard- 
ness with  durability.  Each  consists  of  two  pieces,  one  of  which 
has  a  cylindrical  hole  drilled  through  it  to  receive  the  pivot,  the 
other  is  a  flat  piece,  making  the  rest  or  stop  which  forms  the  bot- 
tom of  the  hole.  Both  stones  are  ground  circular  on  the  edge, 
and  are  fitted  and  burnished  into  small  brass  rings,  which  are 
fastened  into  the  bearings  above  and  below  by  two  small  screws 
applied  to  each.  The  addition  of  jewels  to  a  watch  is  a  great 
advantage,  as  they  do  not  tend  to  thicken  the  oil,  which  brass 
is  apt  to  do,  in  consequence  of  the  oxidation  of  the  metal. 


Cumming's  Elements  of  Clock  and  Watch  Work,  4to.  1766;— Ber- 
THOUD  Histoire  de  la  Mesure  du  Temps  par  les  Horloges,  2  torn.  4to. 
1802; — Harrison  on  Clock  Work  and  Music,  8vo.  1775; — Robison's 
Mechanical  Philosophy,  article  Watch  Work,  vol.  iv. ; — Martin's 
Circle  of  Mechanical  Arts,  4to.  1818 ; — And  the  Encyclopedias  of 
Brewster,  Rees,  and  Nicholson,  under  various  heads. 


CHAPTER  XVII. 


ARTS  OF  METALLURGY. 

The  term  metallurgy,  in  its  most  comprehensive  sense,  sig- 
nifies the  art  of  working  metals  in  every  different  way.  In  a 
more  precise  and  limited  sense,  it  is  confined  to  the  separating 
of  metals  from  their  ores,  and  assaying  them  to  ascertain  their 
value.  In  the  present  chapter,  it  is  proposed  to  make  use  of 
the  term  in  its  more  general  meaning,  so  far,  at  least,  as  to 
comprehend  certain  processes  in  the  management  and  manu- 
facture of  metals,  v/hich  are  sufficiently  interesting  to  merit 
the  attention  of  the  general  student. 

Extraction  of  Metals. — Metals  are  found  in  nature  in  various 
states.  When  uncombined,  or  when  combined  only  with  each 
other,  they  are  said  to  be  in  a  native  state.  When  combined 
with  other  substances,  so  that  the  metallic  properties  are  in  some 
measure  disguised,  they  are  said  to  be  mineralized,  or  in  the 
state  of  ore.  The  substance  with  which  the  metal  is  combined, 
is  termed  its  mineralizer.  The  most  common  states  of  com- 
bination in  which  the  metallic  ores  are  found,  are  oxides,  com- 
binations of  oxides  with  carbonic,  sulphuric,  muriatic,  and 
phosphoric  acids;  and  sulphurets.  These  ores  occur  under 
various  forms,  sometimes  crystallized,  and  often  destitute  of 
any  regular  figure.  They  are  met  with,  generally,  in  veins, 
penetrating  the  strata ;  and  in  this  case,  are  usually  blended  or 
intermixed  with  various  earthy  fossils,  as  calcareous  spar, 
fluor  spar,  quartz,  &ic.  The  accompanying  fossil  is  termed 
the  ganguc  or  matrix  of  the  metal.  Some  metallic  ores  occur 
in  beds,  or  in  large  insulated  masses. 

To  separate  the  metal,  after  it  is  dug  from  the  mine,  the 
mass  is  broken  up  and  subjected  to  the  operations  of  sorting, 
49 


38G 


AirrS    OF  METALLURGY. 


Stamping,  washing,  roasting,  smelting,  and  refining.  Sorting 
consists  merely  in  the  separation  of  the  different  pieces  of  ore 
into  lots,  according  to  the  products  they  are  expected  to  afford, 
and  the  treatment  they  are  likely  to  require.  After  the  ore  is 
sorted,  it  is  carried  to  the  stamper,  or  stamping  mill,  which  has 
been  described  in  a  former  chapter.  The  process  of  stamp- 
ing, breaks  and  pounds  up  the  ore,  together  with  its  gangue,  in- 
to a  coarse  powder.  From  the  stamping  mill,  the  pounded 
ore  is  conveyed  to  the  washing,  a  process  in  which  advan- 
tage is  taken  of  the  difference  of  specific  gravity.  The  oper- 
ation of  washing,  is  sometimes  performed  by  hand,  in  wooden 
vessels,  or  in  troughs  which  cross  a  current  of  water ;  and 
sometimes,  if  the  ore  is  rich  and  valuable,  upon  inclined  tables 
covered  with  cloth.  In  this  process  the  heavier  parts  con- 
sisting of  the  metallic  ore,  sink  first  to  the  bottom,  while  the 
stony  matter,  which  is  lighter  than  the  ore,  being  longer  in 
sinking,  is  carried  farther  down  the  current,  and  thus  separated 
from  the  rest. 

The  next  operation,  which  is  that  of  roasting,  is  employed 
to  drive  off  the  sulphur,  arsenic,  and  other  volatile  parts  which 
the  mineral  may  contain.  It  is  performed  in  a  variety  of  ways, 
and  by  different  processes,  according  to  the  natui-e  of  the  ore, 
and  the  degree  of  heat  required.  The  roasting  is  sometimes 
performed  in  the  air,  and  sometimes  in  furnaces,  among  the 
fuel.  Smelting  consists,  in  general,  in  fusing  the  roasted  ore, 
with  a  view  to  extract  the  metal,  though  the  term  is  sometimes 
applied  to  the  melting  of  metal  in  any  state,  especially  iron. 
The  immediate  object  of  this  process  is  to  reduce  the  metal,  or 
to  separate  the  oxygen  with  which  the  metal  has  either  been 
naturally  combined,  or  has  united  during  the  operation  of  roast- 
ing. This  is  done,  by  placing  in  a  furnace  alternate  layers  of 
charcoal,  or  coke,  and  of  the  metallic  matter  ;  a  strong  heat  is 
then  excited  by  bellows  5  the  carbonaceous  matter  attracts  the 
oxygen,  while  the  metal  is  reduced,  melted,  and  run  out  at  the 
bottom  of  the  furnace.  The  volatile  metals  are  obtained  by 
sublimation  or  distillation.    Even  after  these  operations,  the 


ARTS   OF  MKTALLUKf^V. 


387 


metal  is  seldom  pure,  but  is  combined  with  some  other  metal, 
or  metals,  which  have  been  present  in  the  ore.  If  these  are 
in  small  quantity,  and  do  not  injure  the  metal,  they  are  in  gen- 
era] disregarded.  If  it  is  necessary,  however,  to  separate  them, 
or  if,  from  their  value,  the  separation  is  an  object  of  importance, 
different  processes  are  followed,  adapted  to  each  particular 
metal.  All  the  operations  subsequent  to  smelting,  are  compre- 
hended under  the  general  name  of  refining,  because  their  ef- 
fect is  always  to  obtain  a  purer  metal.  The  different  metals 
are  refined  by  different  processes. 

Assaying. — The  art  of  assaying  metallic  ores,  is  that  of  an- 
alysing them  in  small  quantities,  so  as  to  discover  their  compo- 
nent parts.  It  requires  a  knowledge  of  the  relations  of  the 
metals  to  the  other  chemical  agents,  and  is  varied  in  its  different 
stages  as  applied  to  each.  The  general  process  consists  in  se- 
lecting proper  specimens  of  the  ore,  which  is  done  by  taking 
equal  portions  of  that  which  appears  to  be  the  richest,  the 
poorest,  and  of  medium  value,  and  reducing  these  to  coarse 
powder,  which  is  washed  to  carry  off  any  earthy  or  stony  mat- 
ter. It  is  then  roasted  in  a  shallow  earthen  vessel  under  a  muf- 
fle, to  expel  the  volatile  principles.  It  is  lastly  reduced,  by 
mixing  it  with  fluxes,  and  applying  a  more  or  less  intense  heat, 
as  the  metal  is  more  or  less  refractory.  The  metallic  matter 
existing  in  the  ore  is  thus  obtained.  This,  it  is  obvious,  may 
consist  of  various  metals,  and  if  there  is  reason  to  believe  this, 
and  it  be  of  importance  to  ascertain  it,  it  is  submitted  to  opera- 
tions adapted  to  the  metals  which  may  be  supposed  present. 
Sometimes,  an  accurate  analysis  is  made  at  once  of  the  metal- 
lic ore  in  the  humid  way ;  the  metal  being  dissolved  by  the 
different  acids,  and  precipitated  by  the  alkalis,  earths,  and  oth- 
er re-agents.  The  assaying  of  the  precious  metals  is  usually 
confined  to  ascertaining  the  quantity  of  gold  or  silver  in  any 
alloy  or  compound,  without  regard  to  the  other  constituents. 

Alloys. — The  metals  are  capable  of  combining  with  each 
other  by  fusion,  and  to  these  combinations,  the  name  of  alloy 
is  given.    They  all  retain  the  general  metallic  properties, — 


388 


AR'IS   OF  METALLURGY. 


lustre,  opacity,  and  density,  and  even,  in  the  greater  number  of 
cases,  the  properties  of  the  constituent  metals  remain  in  the 
combination,  only  somewhat  modified.  In  general,  alloys  are 
more  hard  and  britde  than  the  individual  metals  of  which  they 
consist,  though  this,  as  well  as  the  other  changes  of  properties, 
is  considerably  influenced  by  the  proportions  in  which  the  in- 
gredients are  combined.  They  have  also  in  general  a  greater 
fusibility  than  the  mean  fusibility  of  the  respective  metals. 
The  alloys  of  quicksilver,  called  amalgams,  are  usually  soft,  or 
liquid,  according  to  the  proportions.  The  metals  combined  in 
alloys  are  generally  more  susceptible  of  oxidizement  than  in 
their  separate  state,  owing  probably  to  the  diminution  in  the 
powder  of  cohesion,  by  the  combination,  or  perhaps  to  an  elec- 
trical action.  From  their  peculiar  properties,  some  of  the  alloys 
are  extensively  used,  as  brass,  which  is  an  alloy  of  copper  and 
zinc  ;  and  pewter,  which  is  an  alloy  of  tin  and  zinc,  or  lead. 

A  degree  of  condensation  usually  attends  these  combinations, 
so  that  the  specific  gravity  of  the  alloy  is  greater  than  the  mean 
specific  gravity  of  its  constituent  metals.  In  brass,  for  exam- 
ple, it  is  one  tenth  greater,  and  in  some  cases,  the  condensa- 
tion is  such,  that  the  density  is  even  greater  than  that  of  the 
heavier  metals  combined,  as  in  the  alloy  of  silver  and  quick- 
silver. Sometimes,  however,  the  particles  assume  such  an  ar- 
rangement, that  the  density  is  less  than  the  mean,  as  in  the  ex- 
amples of  the  alloy  of  copper  with  silver,  and  of  gold  with 
tin,  and  gold  with  iron. 

In  these  combinations,  there  exists  a  certain  order  of  attrac- 
tions, by  which  one  metal  is  more  disposed  to  unite  with  anoth- 
er, than  a  third  is.  The  difference,  however,  is  not  very 
considerable  ;  hence,  three,  four,  or  more  metals  can  be  com- 
bined together.  Some,  however,  are  difficult  to  unite,  as  iron  and 
lead,  and  iron  and  quicksilver.  The  combination  seems  to  be 
in  some  measure  regulated  by  the  relations  of  fusibility  and 
specific  gravity  ;  so  that  the  affinities  being  equal,  the  metals 
are  less  disposed  to  combine,  as  they  difier  more  in  their  fusi- 
bility and  specific  gravity ;  and  where  the  affinity  is  weak,  a 


ARTS   OF    MKTALLUJKiV.  389 

considerable  difference  of  this  kind  may  prevent  any  combina- 
tion whatever. 

GOLD. 

Gold  exists  in  various  minerals,  but  the  greatest  part  of  the 
gold  in  the  possession  of  mankind,  has  been  found  in  the  form 
of  grains  and  small  masses,  among  the  alluvial  sands  which 
constitute  certain  plains,  and  margins  of  rivers.  In  this  state 
it  is  usually  alloyed  with  small  portions  of  other  metals,  partic- 
ularly silver  and  copper. 

Extraction. — When  native  gold  is  found  in  a  state  of  mixture 
with  foreign  matters,  its  extraction  is  commonly  performed 
by  amalgamation  with  quicksilver.  After  having  been  freed, 
by  pounding  and  washing,  from  most  of  the  stony  matter 
mixed  with  it,  it  is  triturated  whh  ten  times  its  weight  of  quick- 
silver, until  an  amalgam  is  formed.  This  is  separated  from 
any  superfluous  earthy  matter,  and  subjected  to  pressure,  in- 
closed in  leather,  by  which  the  more  fluid  part  is  separated  and 
forced  through  the  leather,  while  the  more  consistent  amalgam, 
containing  the  greater  part  of  the  gold,  remains.  It  is  then 
subjected  to  distillation  in  retorts  of  earthen  ware,  to  separate 
the  quicksilver,  and  the  remaining  gold  is  afterwards  fused. 
When  the  gold  is  contained  in  other  ores,  the  ore  is  roasted  to 
drive  off  the  more  volatile  principles,  and  to  oxidize  the  other 
metals.  The  gold  is  then  extracted  by  amalgamation,  by  li- 
quefaction with  lead,  by  the  action  of  nitric  acid,  or  other 
methods  adapted  to  each  ore,  according  to  its  constituent  parts. 

Cupellation. — Gold  obtained  in  any  of  these  ways,  is  always 
more  or  less  alloyed,  particularly  with  silver  or  copper.  The 
first  step  in  its  purification,  is  the  process  of  cupellation.  To 
explain  the  nature  of  this,  it  is  necessary  to  observe,  that  lead 
is  a  metal  very  fusible,  and  extremely  easy  of  oxidizement, 
forming  an  oxide  which  easily  vitrifies,  and  which  favors  the 
oxidizement  and  vitrification  of  other  metals.  A  portion  of 
lead,  therefore,  is  added  to  the  impure  gold,  more  or  less,  ac- 


390 


ARTS   OF  METALLURGY. 


cording  to  the  quantity  of  alloy  which  it  contains,  of  which  the 
workman  judges  by  the  color,  hardness,  elasticity,  end  specific 
gravity  of  the  gold.  They  are  melted  together,  and  exposed 
to  heat  on  a  cupel,  which  is  a  vessel  made  of  bone  ashes,  or 
sometimes  of  wood  ashes,  under  a  muffle,  or,  in  the  large  way, 
on  the  hearth  of  a  refining  furnace.  The  lead  passes  to  the 
state  of  oxide,  is  vitrified,  and  at  the  same  time  promotes  the 
oxidizement  and  vitrification  of  the  foreign  metals.  The  vitri- 
fied oxide  is  absorbed  by  the  porous  cupel,  or,  in  the  large 
way,  the  greater  part  is  driven  off  by  the  blast  of  bellows,  and 
removed.  When  the  greater  part  of  the  foreign  metals  is  ab- 
stracted, the  remaining  fused  metal  exhibits  various  prismatic 
colors,  which  succeed  each  other  quickly.  It  at  length  sudden- 
ly brightens  and  its  surface  becomes  highly  luminous.  This  is 
regarded  as  the  completion  of  the  process.  The  metal  is  al- 
lowed to  become  solid,  and  while  yet  hot  is  detached. 

Farting. — The  gold,  even  after  having  been  submitted  to 
this  process,  may  still  be  alloyed  with  silver,  which  being  near- 
ly as  difficult  of  oxidizement,  is  not  removed  by  the  action  of 
the  lead.  It  is  therefore  lastly  subjected  to  the  operation  of 
'parting.  The  metal  is  rolled  out  thin,  and  cut  into  small  pie- 
ces. These  are  digested  with  a  moderate  heat  in  diluted  nitric 
acid,  which  dissolves  the  silver,  leaving  the  gold  undissolved  in 
a  porous  mass.  It  has  been  found,  however,  that  when  the 
proportion  of  silver  is  small  to  that  of  gold,  the  latter  protects 
the  former  from  the  action  of  the  acid.  The  previous  step  of 
quartation,  as  it  is  named,  is  therefore  employed,  which  con- 
sists in  fusing  three  parts  of  silv^er  with  one  of  the  gold,  and 
then  subjecting  this  alloyed  metal,  rolled  out,  to  the  operation 
of  the  acid.  These  are  the  operations  employed  in  commerce. 
To  obtain  gold  perfectly  pure,  still  another  process  is  perhaps 
necessary, — dissolving  it  in  nitro-muriatic  acid,  and  adding  to 
the  solution  a  solution  of  sulphate  of  iron,  which,  attracting 
the  oxygen,  precipitates  the  gold  in  the  metallic  state. 

Cementation. — The  process  cementation,  is  performed  by 
beating  the  alloy  into  thin  plates,  and  placing  these  in  alternate 


ARTS   OF  METALLURGY. 


391 


layers,  with  a  cement  containing  nitrate  of  potass,  and  sulphate 
of  iron.  The  whole  is  then  exposed  to  heat,  until  a  great  part 
of  the  alloying  metals  are  removed  by  the  action  of  the  nitric 
acid,  which  is  liberated  by  the  nitre.  Cementation  is  some- 
times employed  by  goldsmiths  to  refine  the  surface  of  articles 
in  which  gold  is  alloyed  with  baser  metals. 

Alloy. — There  is  a  peculiar  language  established  in  com- 
merce, and  often  referred  to  by  writers,  to  denote  the  purity  of 
gold,  or  the  degree  of  its  alloy  with  other  metals.  The  mass 
is  supposed  to  consist  of  24  equal  parts,  these  imaginary  parts 
being  termed  carats.  If  perfectly  pure  or  unalloyed,  it  is  said 
to  be  gold  24  carats  fine;  if  alloyed  with  one  part  of  any  other 
metal,  or  mixture  of  metals,  it  is  said  to  be  23  carats  fine.  In 
this  way  the  proportion  of  alloy  is  expressed.  The  standard 
gold  coin  of  the  United  States  and  Great  Britain,  is  22  carats 
fine,  or  contains  one  twelfth  part  of  alloy. 

Gold,  when  perfectly  pure,  is  not  so  fit  for  coin,  on  account 
of  its  softness,  in  consequence  of  which  the  impression  is  soon 
obliterated,  and  it  sustains  loss  from  friction.  Hence  it  is  al- 
ways alloyed  to  give  it  hardness.  The  metals  that  have  been 
used  for  this  purpose,  are  silver  or  copper.  Gold  made 
standard  by  an  alloy  consisting  of  equal  parts  of  silver  and 
copper,  has  a  color  approaching  more  to  that  of  pure  gold 
than  any  other  alloy.  This  color  also  remains  uniform,  while 
that  with  copper,  after  a  certain  degree  of  wear,  becomes 
unequal.  * 

*  Mr  Hatchet  with  Mr  Cavendish,  subjected  the  different  alloys  that  have 
been  used  as  coin  to  friction,  as  similar  as  possible  to  that  to  which  they  must 
be  subjected  in  the  course  of  circulation.  The  loss  was  by  no  means  consid- 
erable, and  it  appeared  as  the  general  result,  that  the  present  standard  of  gold, 
or  an  alloy  of  one  part  in  12,  is,  all  circumstances  considered,  the  best, 
or  at  least,  as  good  as  any  that  could  be  chosen.  If  the  copper  be  in  larger 
proportions,  more  loss  is  sustained  from  friction.  The  same  alloy  is  employed 
in  the  fabrication  of  plate,  and  of  trinkets,  and  lace,  and,  by  other  additions, 
various  shades  of  color  are  obtained.  Its  alloy  with  a  fifth  part  of  silver, 
forms  the  green  gold  of  the  jewellers,  and  the  addition  of  iron  gives  a 
blue  tint. 


392 


ARTS   OF  METALLURGY. 


Working. — Common  goldsmith's  work  is  performed  by 
casting  in  moulds,  beating  with  hammers,  and  rolling  between 
polished  steel  rollers.  Works  that  have  raised  or  embossed 
figures,  are  commonly  cast  in  moulds  and  afterwards  polished ; 
or  they  are  struck  in  dies,  cut  for  the  purpose.  Vessels  both 
of  gold  and  silver,  are  beat  out  from  flat  plates.  When  the 
form  is  difficult,  they  are  made  of  several  plates  and  soldered 
together.  The  solder  used  for  this  purpose  is  an  alloy  of  gold 
with  silver,  copper,  or  brass.  Small  ornamental  works  are 
commonly  executed  by  enchasing.  This  process  is  performed 
upon  thin  plates  of  gold,  with  a  block  and  hammer.  It  consists 
in  driving  in  portions  of  the  metal  on  one  side  in  such  a  manner 
that  they  stand  in  relief,  forming  the  figures  required  on  the 
opposite  side.  Many  small  articles  are  also  made  from  gold 
wire,  variously  wrought  and  ornamented. 

Gold  Beating. — The  great  utility  of  gilding  in  the  arts,  in 
furnishing  an  incorruptible  covering  to  various  substances,  has 
given  rise  to  an  extensive  consumption  of  gold  leaf,  which  is 
formed,  by  beating  the  metal  to  a  state  of  extreme  tenuity. 
The  gold  is  first  forged  into  plates  on  an  anvil,  and  then  reduc- 
ed, by  passing  it  between  polished  steel  rollers,  till  it  becomes  . 
a  ribband  as  thin  as  paper.  This  ribband  is  divided  into  small 
pieces,  which  are  again  beat  upon  an  anvil  till  they  are  about 
an  inch  square,  after  which  they  are  thoroughly  annealed.  * 
Two  ounces  of  gold  make  150  of  these  squares.  All  these 
squares  are  interlaid  with  leaves,  first  of  vellum,  and  afterwards 
of  gold  beater's  skin,  a  thin  membranous  substance,  obtained 
from  the  intestines  of  animals.  The  whole  is  then  beaten  with 
a  heavy  hammer  till  the  gold  is  extended  to  the  same  size  as 
the  pieces  of  skin.  The  gold  leaves  are  then  taken  out,  and 
each  cut  into  four  parts,  and  the  600  pieces  thus  produced,  are 
again  interlaid  in  the  same  manner  with  skins,  and  the  beating 

*  The  process  of  annealing  is  applied  to  metals  and  some  other  substances 
to  diminish  their  brittleness,  or  increase  their  flexibility  and  ductility.  It 
is  performed  by  heating  the  substance,  and  suffering  it  to  cool  in  a  very 
gradual  manner. 


ARTS   OF  METALLURGY. 


393 


repeated  with  a  lighter  hammer.  They  are  afterwards  redi- 
vided  as  before,  and  formed  into  parcels  which  are  separately 
beat,  at  one  or  more  operations,  until  the  leaf  has  attained  the 
requisite  thinness.  The  use  of  the  membranes  which  are  in- 
terposed between  the  leaves,  is  to  prevent  them  from  cohering 
together,  at  the  same  time  that  they  are  permitted  to  expand  ; 
and  also  to  soften  the  blows  of  the  hammer.  Notwithstanding 
the  vast  extent  to  which  gold  is  beaten  between  these  skins, 
and  the  great  tenuity  of  the  skins  themselves,  yet  they  are  said 
to  sustain  continual  repetitions  of  the  process  for  a  long  time 
without  receiving  injury.  The  kind  of  leaf  called  'party  gold, 
is  formed  by  laying  a  thin  leaf  of  gold,  upon  a  thicker  one  of 
silver.  They  are  then  heated  and  pressed  together  till  they 
unite  and  cohere,  after  which  they  are  beaten  into  leaves  as 
before. 

Gilding  on  Metals. — Gilding  on  copper  is  commonly 
performed  with  an  amalgam  of  gold  and  mercury.  The 
surface  of  the  copper,  being  freed  from  oxide,  is  covered 
with  the  amalgam,  and  afterwards  exposed  to  heat  till  the 
mercury  is  driven  off,  leaving  a  thin  coat  of  gold.  It  is  also 
performed  by  dipping  a  linen  rag  in  a  saturated  solution  of 
gold,  and  burning  it  to  tinder.  The  black  powder  thus  obtain- 
ed is  rubbed  on  the  metal  to  be  gilded,  with  a  cork  dipped  in 
salt  water,  till  the  gilding  appears.  Iron  or  steel,  is  gilded  by 
applying  gold  leaf  to  the  metal,  after  the  surface  has  been  well 
cleaned,  and  heated  until  it  has  acquired  the  blue  color,  which 
at  a  certain  temperature  it  assumes.  The  surface  is  previously 
burnished,  and  the  process  is  repeated  when  the  gilding  is  re- 
quired to  be  more  durable.  It  is  also  performed  by  diluting 
the  solution  of  gold  in  nitro-muriatic  acid,  with  alcohol,  and 
applying  it  to  the  clean  surface.  * 

"  This  last  process  has  been  improved  by  Mr  Stoddart.  A  saturated  solution 
of  gold  in  nitro-muriatic  acid,  being  mixed  with  three  times  its  weight  of  sul- 
phuric ether,  dissolves  the.  muriate  of  gold,  and  the  solution  is  separated 
from  the  acid  beneath.  To  gild  the  steel,  it  is  merely  necessary  to  dip  it,  the 
surface  being  previously  well  polished  and  cleaned,  in  the  ethereal  solution, 

50 


394 


ARTS  OF  METALLURGY. 


Gold  Wire. — The  common  gold  or  gilt  wire,  is  in  reality 
silver  wire  covered  with  gold.  In  making  it,  a  silver  rod  is 
enclosed  in  thick  leaves  of  gold.  It  is  then  drawn  successive- 
ly through  conical  holes  of  different  sizes,  made  in  plates  of 
steel,  in  a  manner  similar  to  that  pursued  in  making  iron  wire. 
The  wire  may  thus  be  reduced  to  an  extreme  degree  of  fine- 
ness, the  gold  being  drawn  out  with  the  silver,  and  constituting 
a  perfect  coating  to  the  wire.  When  it  is  intended  to  be  used 
in  forming  gold  thready  the  wire  is  flattened  by  passing  it  be- 
tween rollers  of  polished  steel.  The  coating  of  gold  remains 
unbroken,  though  so  far  reduced  by  these  processes  as  not  to 
occupy  the  millionth  part  of  an  inch  in  thickness.  The  gold 
thread  commonly  used  in  embroidery,  consists  of  threads  of 
yellow  silk,  covered  by  flattened  gilt  wire,  closely  wound  upon 
them  by  machinery. 


SILVER. 

Extraction. — Silver  is  in  general  extracted  without  much 
difficulty.  When  native,  it  is  separated  from  the  earthy  matter 
by  washing,  and  amalgamation  with  mercury ;  the  latter  being 
separated  again  by  distillation.  When  alloyed  with  antimony, 
or  arsenic,  or  when  mineralized,  the  ore  is  roasted  to  expel  these 
metals,  with  the  sulphur,  or  other  volatile  principles ;  and  the 
residual  matter  is  fused  with  lead,  and  refined  by  cupellation, 
in  a  manner  similar  to  that  described  under  the  head  of 
gold  ;  the  alloy  of  lead  and  silver  being  exposed  to  heat  on 
the  hearth  of  the  refining  furnace,  the  lead  being  oxidized 
along  with  the  foreign  metals,  the  oxidizement  and  vitrification 
of  which  it  promotes,  and  the  vitrified  oxide  being  in  part  ab- 
sorbed, and  in  part  driven  off  by  the  blast  of  the  bellows. 
The  appearance  of  a  vivid  incandescence,  or  brightening,  de- 
notes when  the  silver  has  become  sufficiently  pure.  It  retains 
a  little  gold  in  combination,  but  this  does  not  alter  its  qualities, 

for  an  instant ;  and  on  withdrawing  it,  to  wash  it  instantly  by  agitation  in  wa- 
ter.   By  this  method  steel  instruments  are  very  commonly  gilt. 


ARTS   OF  METALLURGY. 


39d 


and  the  quantity  is  seldom  such,  as  to  render  its  separation,  by 
the  operation  of  parting,  an  object  of  importance. 

If  the  ore  which  is  wrought  contain  only  a  small  portion  of  sil- 
ver, the  previous  operation  of  eliquation  is  sometimes  performed 
on  it.  This  consists  in  adding  a  certain  portion  of  lead  to  the  me- 
tallic matter  which  remains  after  roasting  and  fusing  the  ore. 
This  alloy  is  then  exposed  to  a  degree  of  heat  just  sufficient  to 
melt  the  lead,  which  runs  out,  and  from  its  affinity  to  the  silver, 
carries  it  along  with  it,  leaving  the  copper,  or  other  metals  with 
which  the  silver  had  been  combined.  The  alloy  of  silver  and 
lead  is  then  subjected  to  the  usual  refining  process. 

Working, — Silver  is  cast  into  bars,  or  ingots,  and  afterwards 
wrought  by  hammering  and  rolling.  The  bars  are  beaten  up- 
on anvils,  being  heated  from  time  to  time  to  render  them  more 
ductile.  The  hammering  is  conducted  while  the  heat  is  below 
redness.  They  are  then  passed  between  polished  steel  rollers, 
until  they  are  reduced  to  plates  of  a  suitable  thickness.  To 
form  utensils  of  different  kinds,  these  plates  are  hammered  in 
moulds  till  they  acquire  the  proper  shape.  Vessels  are  often 
made  in  pieces,  which  are  afterwards  united  by  soldering.  The 
solder  used  for  silver,  consists  of  an  alloy  of  silver  with  more 
than  an  equal  part  of  copper  or  brass.  Figures  which  are 
raised  upon  the  silver,  are  produced  by  hammering  the  metal 
upon  steel  dies,  in  which  the  figure  is  cut,  or  by  passing  it 
through  engraved  rollers.  Silver  is  polished  by  burnishing  it 
with  steel  instruments,  or  with  hard  polished  stones ;  and  by 
rubbing  it  with  the  oxide  of  iron  called  colcothar,  in  fine  powder. 

Silver,  in  the  arts,  is  usually  alloyed  with  a  little  copper, 
which  increases  its  hardness,  and  renders  it  more  sonorous 
without  debasing  its  color.  The  standard  silver  of  the  British 
coins  contains  18  pennyweights  of  copper  in  a  pound  Troy  of 
silver;  and  in  the  United  States  1664  grains  of  silver  contain 
179  grains  of  copper. 

Coining. — The  coining  of  silver,  and  other  metals,  was 
originally  performed  by  the  hammer,  in  matrices,  or  dies,  en- 
graved for  the  purpose.    At  the  present  day,  coins  of  every 


396 


ARTS  OP  METALLURGY. 


description  are  more  commonly  milled.  In  coining  by  the 
mill,  the  bars,  or  ingots,  of  gold  or  silver,  after  having  been  cast, 
are  taken  out  of  the  moulds  and  their  surfaces  cleaned.  They 
are  then  flattened  by  rollers,  and  reduced  to  the  proper  thick- 
ness to  suit  the  species  of  money  about  to  be  coined.  To 
render  the  plates  more  uniform,  they  are  sometimes  wire 
drawn,  by  passing  them  through  narrow  holes  in  a  steel  plate. 
The  plates,  whether  of  gold,  silver,  or  copper,  when  reduced 
to  their  proper  thickness,  are  next  cut  out  into  round  pieces 
called  blanks  or  planchets.  This  cutting  is  performed  by  a 
circular  steel  punch  of  the  size  of  the  coin,  which  is  driven 
downward  by  a  powerful  screw,  and  passes  through  a  corres- 
ponding circular  hole,  carrying  before  it  the  piece  of  metal 
which  is  punched  out.  The  pieces  which  are  thus  cut,  are 
brought  to  the  standard  weight,  if  necessary,  by  filing  or  rasp- 
ing ;  and  the  deficient  pieces,  together  with  the  corners  and 
pieces  of  the  plates  left  by  the  circles,  are  returned  to  the 
melter. 

The  milling,  by  which  the  inscription,  or  other  impression,  is 
given  to  the  edge  of  the  coin,  is  performed  by  rolling  the  coin 
edgewise,  between  two  plates  of  steel,  in  the  form  of  rulers, 
each  of  which  contains  half  of  the  engraved  edging.  One  of 
these  plates  is  fixed,  and  the  other  is  moveable  by  a  rack  and 
pinion.  The  coin,  being  placed  between  them,  is  carried 
along  by  the  motion  of  the  rack,  till  it  has  made  half  a  revolu- 
tion and  received  the  whole  impression  on  its  edge.  The  most 
important  part  of  the  coining  still  remains  to  be  done,  and 
consists  in  stamping  both  sides  with  the  appropriate  device,  or 
figure  in  relief.  For  this  purpose,  the  circular  piece  is  placed 
between  two  steel  dies  upon  which  the  figures  to  be  impressed 
are  sunk,  or  engraved  in  the  manner  of  an  intaglio.  The  two 
dies  are  then  forcibly  pressed  together,  by  the  action  of  a  pow- 
erful screw,  to  which  is  attached  a  heavy  transverse  beam, 
which  serves  the  purpose  of  a  fly,  and  concentrates  the  force 
at  the  moment  of  the  impression.  The  coin  is  now  finished 
and  is  thrown  out  when  the  screw  rises. 


ARTS  OF  METALLURGY. 


397 


In  the  coining  machinery  erected  by  Bouhon  and  Watt,  and 
introduced  at  the  mint  in  England,  the  process  is  performed  by 
steam  power,  and  both  the  edges  and  faces  of  the  money  are 
coined  at  the  same  time.  *  By  means  of  this  machinery,  eight 
presses  attended  by  boys,  can  strike  19,000  pieces  of  money 
in  an  hour,  and  an  exact  register  is  kept  by  the  machine  of  the 
number  of  pieces  struck. 

For  the  coining  of  medals  the  process  is  nearly  the  same  as 
for  that  of  money.  The  principal  difference  consists  in  this, 
that  money  having  but  a  small  relief,  receives  its  impressions 
at  a  single  stroke  of  the  engine  ;  whereas  in  medals,  the 
high  relief  makes  several  strokes  necessary ;  for  which  purpose 
the  piece  is  taken  out  from  between  the  dies,  heated,  and  re- 
turned again.  This  process  for  medallions  is  sometimes  re- 
peated as  many  as  a  dozen  or  more  times  before  the  full  im- 
pression is  given  them.  Some  medallions,  in  a  very  high  re- 
lievo, are  obliged  to  be  cast  in  sand,  and  afterwards  perfected 
by  being  sent  to  the  press. 

Plating, — The  great  value  of  silver,  and  the  useful  property 
which  it  possesses  of  resisting  oxidation,  has  given  rise  to  the 
art  of  plating,  in  which  vessels  and  utensils  of  other  metals, 
but  chiefly  of  copper,  are  covered  with  a  thin  coating  of  silver, 
so  as  to  protect  them  from  the  influence  of  the  atmosphere. 
Plating  is  sometimes  executed  by  heating  the  articles  which 
are  to  be  coated,  and  rubbing  on  them  portions  of  leaf  silver, 
with  a  steel  burnisher,  till  it  adheres.  But  it  is  performed  in  a 
better  manner,  by  plating  solid  ingots  of  copper,  and  afterwards 
working  these  into  any  shape  desired.  The  ductility  of  the 
coating  of  silver  causes  it  to  be  extended,  and  drawn  out  with 
the  copper,  so  that  the  latter  metal  never  appears  at  the  surface. 
The  copper  used  in  plating,  is  alloyed  with  a  little  brass. 
Great  care  is  taken  in  casting,  to  form  the  ingots  sound,  and 
free  from  pores  or  flaws.  The  surface  of  the  ingot  is  cleaned 
with  a  file,  and  a  thin  plate  of  silver  is  applied  to  one, 

*  A  particular  account  of  this  machinery  is  given  in  the  London  Mechanic's 
Magazine,  vol.  iii. 


398 


ARTS  OP  METALLURGY. 


or  to  both  sides,  according  to  the  article  to  be  manufactured. 
A  saturated  solution  of  borax  is  then  insinuated  between  the 
edges,  the  object  of  which  is  to  protect  the  copper  from  oxi- 
dation, which  would  otherwise  prevent  the  silver  from  adher- 
ing. The  ingot  is  then  carried  to  the  furnace,  and  exposed  to 
heat  until  the  metals  adhere  to  each  other.  Their  adhesion  is 
owing  to  the  formation  of  an  alloy  between  the  silver  and  cop- 
per, which  being  fusible  at  a  lower  temperature  than  either  of 
the  metals,  acts  as  a  solder  to  unite  them  together.  The  ingot 
is  then  rolled  into  sheets,  by  passing  it  repeatedly  between  iron 
rollers,  annealing  it  from  time  to  time,  as  it  becomes  hard  and 
brittle. 

The  plated  sheets  which  are  thus  obtained,  are  formed  into 
articles  of  different  kinds,  by  hammering  them  in  moulds  cor- 
responding to  the  intended  shape.  When  vessels  are  to  be 
made,  they  are  formed  in  pieces  of  a  convenient  shape,  and 
these  are  soldered  together  with  an  alloy  of  silver,  copper,  and 
brass.  Mouldings,  and  other  ornamental  parts,  are  made  by 
hammering  the  metal  in  steel  dies,  or  rolling  it  between  steel 
rollers,  upon  which  the  pattern  is  cut.  As  the  edges  of  plated 
ware  are  most  liable  to  be  injured  by  wear,  they  are  commonly 
protected  by  what  are  called  silver  edges.  These  are  formed 
of  a  shell  of  silver,  rolled  out,  or  hammered  in  dies,  and  having 
its  inside  filled  up  with  a  mixture  of  tin  and  lead.  When  fin- 
ished, these  edges  are  soldered  to  the  vessel.  The  handles, 
feet,  and  solid  parts  of  vessels,  are  often  made  in  the  same 
way.  Plated  baskets  and  other  light  articles  are  made  from 
copper  cylinders  covered  with  silver,  and  afterwards  drawn  in- 
to wire. 

Plating  on  iron,  as  it  is  used  for  the  buckles  of  harnesses 
and  other  ornaments,  is  executed  by  first  covering  the  iron 
with  a  coating  of  tin,  and  then  applying  closely  to  the  surface 
a  thin  plate  of  silver.  The  union  is  effected  by  a  moderate 
heat,  sufficient  to  melt  the  tin,  and  form  an  alloy  ;  and  it  is 
aided  by  the  use  of  a  resinous  flux. 


ARTS  OF  METALLURGY. 


399 


COPPER. 

Extraction, — The  various  sulphurets  of  copper  are  the  most 
abundant  of  its  ores,  and  of  these  the  most  so  is  copper  pyrites. 
The  malachite,  red  copper  ore,  and  others,  are  generally  asso- 
ciated with  these  in  small  quantities.  Copper  mines  are  wrought 
in  many  countries,  but  those  of  Sweden  are  said  to  furnish 
the  purest  copper  of  commerce.  The  sulphurets  are  the 
ores  from  which  copper  is  usually  extracted.  The  ore  is  roast- 
ed by  a  low  heat,  in  a  furnace  with  which  flues  are  connected, 
in  which  the  sulphur,  that  is  volatilized,  is  collected.  The  re- 
maining ore  is  then  smelted  in  contact  with  the  fuel.  The  iron 
present  in  the  ore,  not  being  so  easily  reduced,  or  fused,  as  the 
copper,  remains  in  the  scoria,  while  the  copper  is  run  out.  It 
often  requires  repeated  fusions,  and  even  after  these,  it  may  be 
still  alloyed  with  portions  of  metals,  which  are  not  volatile,, 
and  are  of  easy  fusion.  Hence  the  copper  of  commerce  is 
never  altogether  pure,  but  generally  contains  a  little  lead,  and 
a  smaller  portion  of  antimony. 

The  carbonates  of  copper  reduced  by  fusion,  in  contact 
with  the  fuel,  afford  a  purer  copper,  as  does  also  the  solution 
of  sulphate  of  copper  which  is  met  with  in  some  mines,  the 
copper  being  precipitated  in  its  metallic  state,  by  immersing 
iron  in  the  solution.  The  precipitate  which  is  thus  formed,  is 
afterwards  fused. 

Working, — Copper,  being  ductile  and  easily  wrought,  is 
applied  to  many  useful  purposes.  It  is  formed  into  thin  sheets 
by  being  heated  in  a  furnace,  and  subjected  to  pressure 
between  iron  rollers.  These  sheets  being  both  ductile  and 
durable,  are  applied  to  a  variety  of  uses,  such  as  the  sheathing 
of  the  bottoms  of  ships,  the  covering  of  roofs  and  domes,  the 
constructing  of  boilers  and  stills  of  a  large  size,  Sic.  Copper 
is  also  fabricated  into  a  variety  of  household  utensils,  the  use 
of  which,  however,  for  preparing  or  preserving  articles  of  food, 
is  by  no  means  free  from  danger,  on  account  of  the  oxidize- 


400 


ARTS   OF  METALLURGY. 


ment,  to  which  copper  is  liable.  It  has  been  attempted  to  ob- 
viate this  danger,  by  tinning  the  copper,  or  applying  to  its  sur- 
face a  thin  covering  of  tin.  This  method  answers  the  purpose 
as  long  as  the  coating  of  tin  remains  entire. 

Copper  may  be  forged  into  any  shape,  but  will  not  bear 
more  than  a  red  heat,  and  of  course  requires  to  be  heated  of- 
ten. The  bottoms  of  large  boilers  are  frequently  forged  with 
a  large  hammer  worked  by  machinery.  The  bolts  of  copper 
used  for  ships,  and  other  purposes,  are  either  made  by  the 
hammer,  or  cast  into  shapes  and  rolled.  The  copper  cylinders 
used  in  calico  printing,  are  either  cast  solid  upon  an  iron  axis, 
or  are  cast  hollow  and  fitted  upon  the  axis.  The  whole  is  af- 
terwards turned,  to  render  the  surface  true. 

Brass, — Brass  is  an  alloy  of  copper  and  zinc.  The  pro- 
portions of  these  two  metals  differ  in  almost  every  place  in 
which  brass  is  manufactured,  and  the  proportion  of  zinc  is 
found  in  different  specimens  to  vary  from  12  to  25  parts  in  a 
hundred.  The  alloy  is  commonly  made  from  the  ores  of  zinc 
mixed  with  copper,  and  with  a  sufficient  quantity  of  charcoal 
to  reduce  them  to  a  metallic  state.  The  volatility  of  the  zinc 
gives  it  a  tendency  to  escape  in  vapor,  on  which  account  the 
combination  is  effected  at  a  lower  heat  than  that  which  would 
be  necessary  to  melt  the  copper.  Several  other  alloys  of  the 
same  metals,  are  also  known  in  the  arts,  differing  in  the  pro- 
portions of  the  ingredients  ;  such  as  pinchbeck,  princess  metal, 
tombac,  Bath  metal,  &ic. 

Manufactures. — The  value  of  brass  in  the  arts,  consists  in 
its  bright  color,  in  its  being  more  fusible  than  copper,  and  in  its 
being  more  easily  wrought  with  common  tools.  In  the  working 
of  brass,  the  larger  articles,  as  well  as  those  of  complicated 
forms,  are  cast  in  moulds.  When  it  is  intended,  for  economy 
of  the  metal,  that  the  article  shall  be  hollow,  as  in  the  case  of 
andirons,  he,  it  is  cast  in  halves,  or  pieces,  which  are  after- 
wards soldered  together,  and  turned  in  a  lathe,  or  otherwise 
polished.  Brass  is  also  rolled  into  thin  sheets,  and  drawn 
into  wire.     A  variety  of  figured  and  ornamental  articles 


ARTS   OF  METALLURCY. 


401 


are  made  by  stamping  it  in  dies  or  moulds.  Brass  knobs  and 
similar  implements,  if  large,  are  made  in  pieces,  and  solder- 
ed. The  wheel  work  of  timepieces,  and  of  other  machinery 
which  is  not  subjected  to  great  strain  or  wear,  is  usually  made 
of  brass.  The  comparative  softness  of  this  alloy,  permits  it 
to  be  cut  with  thin  saws,  and  to  be  turned  in  a  lathe,  with  much 
greater  ease  than  iron. 

Buttons  are  either  struck  out  of  sheets  of  brass  with  a  cir- 
cular punch,  driven  by  a  fly  press,  or  they  are  cast  in  large 
numbers  at  once  in  a  mould,  or  flask  of  sand.  The  eye,  or 
shank,  of  the  button  is  made  separately  by  a  machine,  and 
soldered  on,  if  the  button  has  been  cut  out  by  the  punch.  If 
the  button  is  cast,  the  eye  is  previously  placed  in  the  mould, 
so  that  its  extremity  is  immersed  in  the  centre  of  the  melted 
metal.  If  the  button  is  to  be  plain,  its  surface  is  planished  by 
the  stroke  of  a  smooth  die  ;  and  if  figured,  it  is  stamped  with 
an  engraved  die.  The  edges  are  afterwards  turned  ofl'  in  a 
lathe.  The  gilding  of  brass  buttons  is  performed  by  covering 
them  with  an  amalgam  of  gold  and  mercury,  from  which  the 
mercury  escapes  when  heated,  and  leaves  the  gold.  White 
metal  buttons  are  made  of  an  alloy  of  brass  and  tin,  and  sub- 
sequently coated  with  tin.  The  brass  eyes  of  pearl  buttons 
are  inserted  by  drilling  a  conical  hole,  which  is  largest  on  the 
inside,  in  the  mother  of  pearl,  or  shell,  of  which  the  button  is 
made.  The  eye,  having  an  extremity  like  a  hollow  cone,  is 
then  driven  in,  till  it  spreads  and  fills  the  cavity. 

Pins  are  made  of  brass  wire  cut  into  proper  lengths.  The 
pieces  are  pointed  by  turning  them  with  the  fingers,  upon 
stones,  or  steel  mills.  The  heads  are  cut  from  a  spiral  coil  of 
wire,  in  pieces  of  a  suitable  length  ;  and  after  being  placed 
upon  the  pins,  are  shaped  and  fastened  by  the  stroke  of  an  in- 
strument like  a  hammer.  Several  machines  have  been  invent- 
ed for  this  manufacture,  one  of  which  makes  a  solid  head 
from  the  body  of  the  pin  itself.  Pins  are  whitened  by  immers- 
ing them  in  a  vessel  containing  tin  and  lees  of  wine,  and  are 
pohslied  by  agitating  them  with  bran  in  a  revolving  cask. 
51 


402 


ARTS  OF  METALLURGY. 


Bronze. — A  series  of  alloys  is  formed  from  the  combination 
of  copper  with  tin.  The  combination  appears  to  have  a  ten- 
dency to  form  in  certain  proportions,  regulated  in  some  meas- 
ure by  the  specific  gravities  and  fusibilities  of  the  metals  ;  for 
when  kept  in  fusion,  and  allowed  to  cool  without  agitation,  two 
alloys  are  formed,  the  under  part  of  the  mass  being  one  of 
copper  with  a  small  portion  of  tin,  and  the  upper  part  tin  with 
a  small  proportion  of  copper,  while  between  these  there  is 
probably  a  gradation.  By  agitation,  this  separation  is  counter- 
acted. In  general,  tin  lessens  the  ductility  of  copper,  while 
it  renders  it  more  hard,  rigid,  and  sonorous;  these  qualities  be- 
ing possessed  in  various  degrees  by  the  different  alloys,  accord- 
ing to  their  proportions,  the  hardness  and  brittleness  being 
greater  as  the  tin  predominates.  The  density  of  the  compound 
is  also  always  greater  than  the  mean  density ;  the  contraction 
from  the  combination  being  about  one  eighth.  The  principal 
of  these  alloys,  are  bronze,  gun  metal,  from  which  pieces  of 
artillery  are  cast,  hell  metal,  and  speculum  metal  which  has  been 
used  for  the  mirrors  of  reflecting  telescopes.  Bronze  is  one 
of  those  in  which  the  proportion  of  tin  is  least,  not  exceeding 
10  or  12  parts  in  100.  It  is  of  a  greyish  yellow  color,  harder 
than  copper,  less  hable  to  rust,  and  more  fusible,  so  as  to 
be  easily  cast  in  moulds.  Hence  it  is  employed  in  the 
casting  of  statues.  The  metal  from  which  pieces  of  artillery 
are  cast,  is  of  a  similar  composition,  containing  rather  less  tin. 
It  appears  that  an  alloy  very  similar  to  bronze,  was  much 
in  use  among  the  ancients ;  and  swords,  darts,  and  other  war- 
like instruments  were  formed  of  it,  as  were  also  various  utensils.* 

*  According  to  Dr  Pearson's  experiments  made  on  various  instruments  of 
this  kind,  the  alloy  appears  to  have  consisted  of  about  eight  or  nine  parts  of 
copper,  with  one  of  tin,  and,  as  he  justly  remarks,  this  alloy  still  affords  the 
best  substitute  for  iron  or  steel.  While  the  art,  therefore,  of  manufacturing 
malleable  iron  was  imperfectly  known,  and  difficult  to  be  practised,  it  must 
have  been  much  used.  The  hardness  o\  this  alloy  observed  in  ancient  arms, 
had  even  given  rise  to  an  opinion,  that  the  ancients  were  acquainted  with  a 
method  of  hardening  copper,  which  had  been  lost.  Of  this  alloy,  medals  and 
coins  were  also  often  formed,  as  appears  from  the  experiments  of  Dize,  on 
several  Greek,  Roman,  and  Gallic  coins,  which  consisted  of  copper  and  tin  alone. 


ARTS   OF  METALLURGY. 


403 


When  the  proportion  of  tin  is  increased,  the  alloy  is  render- 
ed more  brittle  and  elastic,  and  at  the  same  time  highly  son- 
orous. Bell  metal  is  an  alloy  of  this  kind,  in  which  the  pro- 
portion of  tin  varies  from  one  third  to  one  fifth  of  the  weight 
of  the  copper,  according  to  the  size  of  the  bell,  and  the  sound 
required. 

When  the  proportion  of  tin  is  still  greater,  an  alloy  is  form- 
ed called  speculum  metal,  which  is  of  a  white  color,  and  which 
from  the  closeness  of  its  texture,  and  its  susceptibility  of  a  fine 
polish,  exceeds  most  metals  in  the  property  of  reflecting  light. 
Hence  it  is  used  in  forming  the  speculum  of  reflecting  teles- 
copes. It  has  also  the  advantage  of  not  being  Hable  to  tarnish 
on  exposure  to  the  air.  The  proportion  in  which  these  quali- 
ties were  best  attained,  appeared,  from  the  experiments  of  Mr 
Mudge,  to  be  a  litde  less  than  one  part  of  tin,  with  two  parts 
of  copper.  ^  The  Chinese  pakfong,  or  white  copper,  which 
is  sometimes  imported  from  that  country,  is  an  alloy,  according 
to  Dr  Fyfe,  of  copper,  zinc,  nickel,  and  iron. 

LEAD. 

Extraction. — Lead  mineralized  by  sulphur,  forms  by  far 
the  most  abundant  ore  of  the  metal,  and  has  been  long  known 
to  mineralogists  by  the  name  of  galena.  This  is  the  ore 
which  is  generally  wrought,  and  from  which  nearly  all  the  lead 

*  Mr  Edwards,  by  an  extensive  series  of  experiments  on  the  proportions  of 
these  metals,  and  the  effects  of  different  additions,  succeeded  in  forming  alloys 
much  superior  in  brightness  to  those  that  had  been  before  used.  That  which 
he  preferred,  was  composed  of  32  ounces  of  copper,  15  or  16  oz.  tin,  according 
to  the  purity  of  the  copper,  to  which  were  added  brass,  arsenic,  and  silver,  of 
each  one  ounce  ;  the  copper  and  the  tin  being  melted  in  separate  crucibles, 
when  in  fusion,  the  one  being  added  to  the  other,  and  the  composition,  when 
well  stirred,  being  poured  into  cold  water.  The  other  metals  are  added  in  a 
second  fusion.  The  arsenic  appears  to  give  a  greater  degree  of  density  and 
compactness  to  thfe  alloy,  the  brass  more  tenacity,  and  the  silver  adds  to  the 
whiteness.  According  to  the  more  recent  experiments  of  Mr  Little,  the  best 
composition,  is  32  parts  of  bar  copper,  four  parts  of  brass,  sixteen  and  a  half 
parts  of  tin,  and  one  and  three  quarters  of  arsenic. 


404 


ARTS  OF  METALLURGY. 


of  commerce  is  procured.  The  ore,  after  being  pounded,  and 
freed  from  the  admixture  of  any  stony  matter  by  washing,  is 
fused  in  a  furnace,  with  the  addition  of  lime,  which  combines 
with  the  sulphur  of  the  sulphuret;  the  lead  is  mehed,  and  run 
out  by  an  aperture  towards  the  bottom  of  the  furnace.  When 
the  native  salts  of  lead  are  found  with  the  galena,  so  as  to  ren- 
der it  of  importance  to  work  them,  they  are  selected  until  a 
sufficient  quantity  be  obtained.  They  are  then  roasted  to  expel 
the  volatile  matter,  and  are  afterwards  fused  in  contact  with 
the  fuel,  with  an  addition  of  lime.  The  lead  obtained  from 
galena,  sometimes  contains  so  much  silver  as  to  be  subjected 
to  an  additional  process  to  separate  the  silver.  In  this  case 
the  lead  is  oxidized  in  a  furnace,  a  current  of  air  being  direct- 
ed on  its  surface  when  in  fusion,  by  bellows.  Towards  the 
end  of  the  operation,  the  silver  remains  with  a  small  portion  of 
lead,  from  which  it  is  freed  by  cupellation  ;  and  the  oxide  of 
lead  is  either  applied  to  the  purposes  for  which  it  is  used,  or  is 
reduced  to  the  metallic  state. 

Manufacture. — Lead,  being  fusible  at  a  low  temperature,  re- 
quires only  to  be  cast  in  smooth  moulds,  to  form  weights,  bul- 
lets, and  other  articles  of  small  size.  The  linings  of  cisterns, 
and  the  coverings  of  roofs,  gutters,  &ic.  are  made  of  sheet 
lead  ;  pumps,  and  aqueducts,  of  leaden  pipes. 

Sheet  lead,  of  the  thicker  kinds,  is  cast  upon  large  tables 
covered  with  sand,  and  having  an  elevated  rim.  The  melted 
lead  is  poured  upon  the  surface  out  of  a  box  which  moves 
upon  rollers  across  the  table,  and  is  spread  out  with  a  uniform 
thickness,  by  passing  over  it  a  straight  piece  of  wood,  called  a 
strike.  The  sheets  thus  cast  are  afterwards  rendered  thinner, 
by  reducing  them  between  rollers.  The  sheet  lead  with  which 
tea  chests  are  hned,  is  an  alloy  of  lead  and  tin,  and  is  made 
by  the  Chinese,  by  suddenly  compressing  the  melted  metal 
between  flat,  polished  stones. 

Lead  pipes,  for  conveying  water,  may  be  made  in  various 
ways.  They  were  at  first  formed  of  sheet  lead  bent  round  a 
cylindrical  bar,  or  mandrel,  and  soldered  5  but  these  pipes  are 


ARTS  OF  METALLURGY. 


405 


liable  to  crack  and  leak,  especially  when  bent.  A  second  me- 
thod is  to  cast  a  short  tube  of  lead  in  a  cylindrical  mould  with 
a  core.  This  tube,  when  cold,  is  drawn  nearly  out  of  the 
mould,  and  a  fresh  portion  of  melted  lead  poured  in  at  aper- 
tures in  the  sides  of  the  mould.  The  melted  lead  unites  with 
the  tube  previously  formed,  so  as  to  increase  its  length,  and  by 
repeating  the  process,  any  length  of  pipe  may  be  produced. 
But  pipes  cast  in  this  manner  are  found  to  have  imperfections 
arising  from  flaws  and  air  bubbles.  A  third  method,  which  is 
now  most  commonly  practised,  is  to  cast  a  short,  thick  tube  of 
lead,  upon  one  end  of  a  long,  polished  iron  cylinder,  or  man- 
drel, of  the  size  of  the  bore  of  the  intended  pipe.  The  lead 
is  then  reduced  in  size,  and  drawn  out  in  length,  either  by 
drawing  it  on  the  mandrel,  through  circular  holes,  of  different 
sizes,  in  a  steel  plate ;  or  by  rolhng  it  between  contiguous  rol- 
lers, which  have  a  semi-circular  groove  cut  round  the  circum- 
ference of  each.  A  fourth  mode  invented  by  Mr  Bramah, 
consisted  in  forcing  melted  lead,  by  means  of  a  pump,  into  one 
end  of  a  mould  ;  while  it  was  discharged  in  the  form  of  a  pipe 
at  the  opposite  end.  Care  was  taken  so  to  regulate  the 
temperature,  that  the  lead  should  chill,  just  before  it  left  the 
mould. 

Leaden  shot,  consist  of  drops  of  metal  which  are  discharg- 
ed in  a  melted  state  from  small  orifices,  and  cool  in  falling. 
The  best  shot  are  cast  in  high  towers  built  for  the  purpose. 
The  lead  is  previously  alloyed  with  a  portion  of  arsenic,  which 
increases  the  cohesiveness  of  its  particles,  and  causes  h  to  as- 
sume more  readily  the  globular  form.  It  is  melted  at  the  top 
of  the  tower,  and  poured  into  a  vessel,  which  is  perforated  at 
bottom  with  numerous  small  holes.  The  lead,  after  running 
through  these  perforations,  immediately  separates  into  drops, 
which  cool  in  falling  through  the  height  of  the  tower,  and  are 
received  in  a  reservoir  of  water  at  bottom,  to  break  the  force 
of  the  fall.  The  shot  are  then  proved  by  rolling  them  down 
an  inclined  board.  Those,  which  are  irregular  in  shape,  roll 
off  at  the  sides,  or  stop,  while  the  spherical  ones  continue  to 


ABTS  OF  METALLURGY. 


the  end.  They  are  then  assorted  by  passing  them  through 
wire  sieves  of  different  fineness.  The  glazing  is  given  by  agi- 
tating them  with  small  quantities  of  black  lead. 

Shot  is  sometimes  made  mechanically  by  cutting  sheets  of 
lead  into  cubes,  and  agitating  these  for  a  long  time  in  a  cylin- 
drical vessel  turned  upon  an  axis.  The  attrition  thus  produc- 
ed, communicates  a  globular  form  to  the  cubes. 

TIN. 

Native  oxide  of  tin,  or  tinstone^  as  it  is  commonly  named, 
is  the  only  ore  that  is  wrought  to  obtain  this  metal.  Being 
freed  by  washing,  from  the  intermixture  of  any  stony  matter, 
it  is  roasted,  and  then  fused  in  contact  with  the  fuel,  by  a  mod- 
erate heat.  The  tin  of  Cornwall  is  supposed  to  be  purer  than 
the  German  tin,  though  it  is  still  inferior  to  the  tin  from  India. 

Block  tin,  consisting  of  the  metal  in  its  solid  state,  is  used 
for  vessels  which  are  not  exposed  to  a  temperature  much  ex- 
ceeding that  of  boiling  water.  Vessels  of  this  kind,  being  not 
readily  tarnished,  form  a  cheaper  substitute  for  silver  and  plated 
ware.  A  kind  of  ware  denominated  Biddery  ware,  consists 
of  tin  vessels  alloyed  with  a  little  copper,  and  having  their  sur- 
face made  black  by  the  application  of  substances  containing 
nitre,  common  salt,  with  sal  ammoniac.  Tin  foil  is  made  by 
rolling,  in  the  same  way  as  the  plates  for  tinned  iron  hereafter 
described.  It  is  also  sometimes  hammered.  The  most  ex- 
tensive use,  however,  to  which  metallic  tin  is  applied,  is  to  form 
a  coating  for  other  metals,  which  are  stronger  than  itself,  but  at 
the  same  time  more  liable  to  oxidation  by  exposure  to  the  air. 

Tin  plates,  which  constitute  the  material  of  the  common  tin 
ware,  so  extensively  used,  are  thin  sheets  of  iron  coated  with 
tin.  The  mode  of  rolling  these  sheets  will  be  described  under 
the  head  of  Iron.  To  prepare  them  for  tinning,  they  are 
steeped  in  water  acidulated  with  muriatic  acid,  and  then  heat- 
ed, scaled,  and  rolled,  to  remove  all  oxide,  and  enable  the  tin 
to  adhere  to  the  iron.    The  tin  is  kept  melted  in  oblong,  rec- 


ARTS  OF  METALLURGV. 


407 


tangular  vessels,  and  to  preserve  its  surface  from  oxidation,  a 
quantity  of  melted  fat  and  oil  is  kept  floating  upon  it.  The 
iron  plates  are  taken  up  with  pincers,  and  immersed  in  the  tin 
for  some  time.  When  withdrawn  they  are  found  to  have  ac- 
quired a  bright  coating  of  the  tin,  which  adheres  closely,  ow- 
ing to  the  formation  of  an  intermediate  alloy.  The  dipping  is 
repeated  twice,  or  more  times,  according  to  the  thickness  of 
the  coat  intended  to  be  given,  and  also  to  produce  a  smooth 
surface,  and  between  these  processes  the  tin  is  equalized  with 
a  brush.  ^ 

Various  other  articles  of  iron,  such  as  spoons,  nails,  bridle 
bits,  small  chains,  &ic.  are  coated  with  tin,  by  immersing  them 
in  that  metal  while  in  a  state  of  fusion.  From  the  affinity  be- 
tween tin  and  copper,  a  thin  layer  of  the  former  metal  can  be 
easily  applied  to  the  surface  of  the  latter ;  and  this  practice  of 
tinning,  as  it  is  named,  is  often  employed  to  prevent  the  erosion 
or  rusting  of  copper  vessels,  and  the  noxious  impregnation 
which  they  would  otherwise  communicate  to  liquors  kept  in 
them.  The  surface  of  the  copper  is  polished  so  as  to  be  quite 
bright ;  sal  ammoniac  is  applied  to  it,  when  hot,  by  which  the 
oxidation  appears  to  be  prevented ;  or  pitch  is  sometimes  used 
for  the  same  purpose.  The  melted  tin,  or  sometimes  an  alloy 
of  tin  and  lead,  is  then  applied  to  the  surface  of  the  copper, 
to  which  it  readily  adheres. 

Silvering  of  Mirrors. — The  surfaces  best  adapted  for  re- 
flecting light,  are  those  of  polished  metals.  To  constitute  a 
good  reflector,  it  is  necessary  that  a  metal  should  be  suscepti- 
ble of  an  equal,  unbroken,  and  exquisite  polish,  and  that  it 
should  retain  this  polish,  without  being  tarnished  by  the  atmos- 
phere. Speculum  metal  is  chiefly  employed  for  reflecting 
surfaces  in  telescopes,  but  for-  common  purposes  an  amalgam 
of  tin  and  mercury  is  used  in  a  state  of  adhesion  to  glass. 
The  use  of  the  glass  is,  in  the  first  place,  to  produce  a  smooth 
surface  in  the  amalgam ;  and  afterwards  to  protect  it  from  oxi- 
dation by  the  atmosphere. 

*  For  a  full  account  of  the  present  mode  of  manufacturing  tin  plate,  see 
Parkes'  Chemical  Essays,  vol.  ii. 


408 


ARTS  OP  METALLURGY. 


In  the  silvering  of  plain  looking  glasses,  a  flat,  horizontal 
slab  of  stone,  is  used  as  a  table.  This  is  smoothly  covered 
with  paper,  and  a  sheet  of  tin  foil,  equal  to  the  size  of  the 
glass,  is  extended  over  it.  A  quantity  of  mercury  is  then  laid 
upon  the  tin  foil,  and  immediately  spread  over  it  with  a  roll  of 
cloth,  or  a  hares  foot.  Afterwards,  as  much  mercury  as  the 
surface  will  hold,  is  poured  on.  While  this  mercury  is  yet  in 
a  fluid  state,  the  plate  of  glass  is  slid  on  at  the  edge  of  the 
table,  so  as  to  pass  over  the  tin  foil,  driving  the  superfluous 
mercury  before  it.  In  this  way  any  bubbles  of  air  and  particles 
of  dust  are  prevented  from  getting  between  the  glass  and  the 
metal,  and  an  uninterrupted  coating  is  formed.  In  order  to 
force  out  the  remaining  liquid  mercury,  the  glass  is  placed 
in  a  sloping  position,  to  allow  the  mercury  to  drain  off,  after 
which  heavy  weights  are  placed  upon  the  glass,  and  suffered 
to  remain  for  some  time.  The  portion  which  is  left,  amalga- 
mates with  the  tin,  and  forms  a  permanent  reflecting  surface, 
the  smoothness  and  perfection  of  which,  depends  upon  the 
degree  of  regularity  and  polish  which  the  glass  possesses. 

In  silvering  concave  and  convex  mirrors,  instead  of  a  stone 
table,  the  tinfoil  is  spread  upon  a  plaster  mould,  previously  cast 
on  the  surface  of  the  glass  itself.  The  inside  of  glass  globes 
is  silvered  by  pouring  into  them  a  fusible  alloy  of  tin,  lead,  bis- 
muth, and  mercury,  the  heat  of  which,  when  liquid,  is  not  suf- 
ficient to  break  the  glass.  By  turning  the  globe  about,  a  thin 
metallic  coating  is  deposited  on  the  whole  interior  surface. 

IRON. 

The  properties  which  iron  possesses  in  its  various  forms, 
render  it  the  most  useful  of  all  the  metals.  The  toughness  of 
malleable  iron,  adapts  it  to  purposes  where  great  strength  is 
required ;  while  its  combination  of  difficult  fusibility  with  the 
property  of  softening  by  heat,  so  as  to  admit  of  forging  and 
welding,  renders  it  capable  of  being  easily  worked,  and  of 
withstanding  an  intense  heat.    Cast  iron,  from  its  cheapness, 


ARTS  OF  METALLURGY. 


409 


and  the  facility  with  which  its  form  is  changed  by  fusion,  is 
made  the  material  of  numerous  structures  and  machines. 
Steel,  which  is  the  most  important  compound  of  iron,  exceeds 
all  other  metals  in  the  combination  of  hardness  and  tenacity  ; 
and  hence  it  is  particularly  adapted  to  the  fabrication  of  cutting 
instruments.  It  is  equally  superior  in  elasticity,  a  quality 
by  which  it  is  suited  to  be  the  spring  of  motion  in  various 
machines. 

Smelting. — The  principal  ores  which  are  wrought  for  the 
extraction  of  iron,  are  the  different  species  of  the  native  ox- 
ides. The  process  is  somewhat  different,  as  carried  on  in  dif- 
ferent countries,  and  as  adapted  to  different  ores  ;  but  the  fol- 
lowing is  the  general  outline  of  it,  as  it  is  conducted  on  the 
haematite,  bog  ores,  and  other  oxides  of  iron. 

The  ore  is  first  roasted  with  a  strong  heat,  to  expel  the  car- 
bonic acid,  and  any  portion  of  sulphur,  or  other  volatile  matter 
that  may  be  present.  The  remaining  ore  is  put  into  a  furnace 
of  a  conical  form  with  charcoal,  or  with  coke,  and  exposed  to 
a  heat  rendered  sufficiently  intense  by  a  blast  of  air  urged 
through  the  furnace.  A  quantity  of  lime  is  at  the  same  time 
added  to  the  ore,  and  fuel ;  the  advantage  of  which  appears  to 
be,  that  in  combination  with  the  argillaceous  and  siliceous  sub- 
stances generally  contained  in  the  iron  ores,  it  acts  as  a  flux, 
to  vitrify  the  foreign  matter,  and  thus  facilitate  the  sepa- 
ration of  the  melted  metal.  The  proportions  of  these  are  ex- 
tremely various,  according  to  the  nature  of  the  ore.  When 
the  furnace  is  once  charged,  the  charge  is  renewed  at  the  up- 
per part,  as  fast  as  the  materials  sink,  and  the  process  is  car- 
ried on  for  a  long  time  without  interruption.  During  this  pro- 
cess, the  oxygen  of  the  oxide  of  iron  unites  with  one  portion 
of  the  carbon,  and  the  metal  with  another,  producing  carbonic 
acid,  and  carburet  of  iron ;  while  the  earthy  substances,  to- 
gether with  a  little  oxide  of  iron,  enter  into  combination,  form- 
ing a  vitreous  substance  called  slag  or  scoria,  and  which  being 
lighter  than  the  metal,  rises  upon  its  surface.  The  slag  is 
drawn  off  by  an  opening,  and  the  melted  metal  is  collected  in 
52 


410 


ARTS   OF  METALLURGY. 


a  cavity  at  bottom,  from  which,  as  it  accumulates,  it  is  convey- 
ed off  at  intervals  into  moulds. 

Crude  Iron. — The  metal  thus  obtained,  is  named  pig  iron, 
and  crude,  or  cast  iron.  It  is  far  from  being  pure,  containing 
always  more  or  less  oxygen  and  carbon  ;  and  often  several  oth- 
er heterogeneous  ingredients,  such  as  manganese,  and  the 
metallic  bases  of  lime,  clay,  and  silex,  with  portions  of  unre- 
duced ore,  and  charcoal.  The  oxygen  is  partly  a  portion  of 
what  was  originally  combined  with  the  metal  in  the  ore,  and 
partly  perhaps,  derived  from  the  blast  of  air,  which  is  driven 
through  the  furnace,  and  necessarily  presented  to  the  metal  in 
a  state  of  fusion.  Hence  the  qualities  of  cast  iron  are  very 
various,  according  as  one  or  other  of  the  principles  predominate. 

Iron  in  this  state,  is  readily  capable  of  being  fused,  and 
cast  into  moulds.  It  is,  however,  much  more  britde  than 
when  pure,  and  cannot  be  wrought,  or  flattened  under  the 
hammer.  Hence  it  is  altogether  unfit  for  many  purposes,  to 
which  pure,  or  malleable  iron  is,  from  its  tenacity,  and  softness, 
well  adapted. 

Casting. — Iron,  as  well  as  brass,  and  other  metals  which  melt 
at  temperatures  above  ignition,  is  cast  in  moulds  made  of  sand. 
The  kind  of  sand  most  employed  is  loam,  which  possesses  a 
sufficient  portion  of  argillaceous  matter,  to  render  it  moderate- 
ly cohesive,  when  damp.  The  mould  is  formed  by  burying  in 
the  sand  a  wooden  pattern,  having  exactly  the  shape  of  the  ar- 
ticle to  be  cast.  The  sand  is  most  commonly  inclosed  in  flasks, 
which  are  square  frames  resembling  wooden  boxes  open  at  top 
and  bottom.  If  the  pattern  be  of  such  form  that  it  can  be 
lifted  out  of  the  sand,  without  deranging  the  form  of  the 
mould,  it  is  only  necessary  to  make  an  impression  of  the  pat- 
tern in  one  flask ;  and  articles  of  this  kind  are  sometimes  cast 
in  the  open  sand  upon  the  floor  of  the  foundry.  But  when 
the  shape  is  such  that  the  pattern  could  "not  be  extracted  with- 
out breaking  the  mould,  two  flasks  are  necessary,  having  half 
the  mould  formed  in  each.  The  first  flask  is  filled  with  sand, 
by  ramming  it  close,  and  is  smoothed  off  at  the  top.  The 


ARTS   OF   METALLURGY.  411 

pattern  is  separated  into  halves,  one  half  being  imbedded  in 
this  flask.  A  quantity  of  white  sand,  or  burnt  sand,  is 
sprinkled  over  the  surface  to  prevent  the  two  flasks  from  co- 
hering. The  second  flask  is  then  placed  upon  the  top  of  the 
first,  having  pins  to  guide  it.  The  other  half  of  the  pattern,  is 
put  in  its  place,  and  the  flask  is  filled  with  sand,  which  of  course 
receives  the  impression  of  the  remaining  half  of  the  pattern  on 
its  under  side.  After  one  or  more  holes  are  made  in  the  top, 
to  permit  the  metal  to  be  poured  in,  and  the  steam  and  air  to 
escape,  the  flasks  are  separated  and  the  pattern  withdrawn. 
When  the  flasks  are  again  united,  a  perfect  cavity,  or  mould, 
is  formed,  into  which  the  melted  metal  is  poured. 

The  arrangement  of  the  mould  is  of  course  varied  for  dif- 
ferent articles.  When  the  form  of  the  article  is  complex  and 
difficult,  as  in  some  hollow  vessels,  crooked  pipes,  &ic.,  the 
pattern  is  made  in  three  or  more  pieces,  which  are  put  together 
to  form  the  mould,  and  afterwards  taken  apart  to  extract  them. 
In  some  other  irregular  articles,  as  andirons,  one  part  is  cast 
first,  and  afterwards  inserted  in  the  flask  which  is  to  form  the 
other  part. 

The  metal  for  small  articles  is  usually  dipped  up  with  iron 
ladles,  coated  with  clay,  and  poured  into  the  moulds.  In  large 
articles,  such  as  cannon,  the  mould  is  formed  in  a  pit  dug  in 
the  earth  near  the  furnace,  and  the  melted  metal  is  conveyed 
to  it  in  a  continued  stream,  through  a  channel  communicating 
with  the  bottom  of  the  furnace. 

Cannon  balls  are  sometimes  cast  in  moulds  made  of  iron, 
and  to  prevent  the  melted  metal  from  adhering,  the  inside  of 
the  mould  is  covered  with  powder  of  black  lead.  Rollers  for 
flattening  iron  are  also  cast  in  iron  cases.  This  method  is  cal- 
led chill  casting,  and  has  for  its  object  the  hardening  of  the 
surface  of  the  metal,  by  the  sudden  reduction  of  temperature, 
which  takes  place  in  consequence  of  the  superior  conducting 
power  of  the  iron  mould.  These  rollers  are  afterwards  turned 
smooth  in  a  powerful  lathe,  which  has  a  slow  motion,  that  the 
cutting  tool  may  not  become  heated  by  the  friction. 


/ 


412  ARTS  OP  METALLURGY. 

Malleable  Iron. — To  obtain  pure  iron,  that  is,  to  free  crude 
iron  from  the  oxygen,  carbon,  and  other  foreign  substances 
contained  in  it,  it  is  subjected  to  two  operations, — melting,  and 
forging.  The  fusion  is  performed  in  different  furnaces.  The 
melted  metal  is  in  some  cases  run  out  to  free  it  from  the  scoria 
wliich  has  separated  ;  and  this  process  is  repeated  until  the 
iron  attains  a  degree  of  consistence  sufficient  to  be  submitted 
to  the  action  of  the  forge  hammer.  But  more  commonly  the 
metal  is  kept  in  fusion  in  a  reverberatory  furnace,  called  a 
puddling  furnace,  where  it  is  raised  to  a  very  high  temperature. 
The  liquid  is  stirred  frequently  to  facilitate  the  combination  of 
the  carbon  and  oxygen.  At  length  a  lambent  blue  flame  ap- 
pears on  its  surface,  probably  from  the  formation  and  disen- 
gagement of  carbonic  oxide,  and  after  some  time  the  fluidity 
of  the  metal  diminishes,  until  it  at  length  assumes  the  consist- 
ence of  a  stiff  paste.  It  is  then  subjected  to  the  action  of  a 
very  large  hammer,  or  to  the  more  equable  pressure  of  rollers, 
by  which  a  portion  of  oxide  of  iron,  carbon,  and  other  hetero- 
geneous substances  not  consumed  during  the  fusion,  are  forced 
out.  The  iron  in  this  state,  is  no  longer  granular  in  its  texture, 
but  is  soft,  ductile,  and  malleable,  and  much  less  fusible.  It  is 
then  named  wrought  iron,  forged,  or  bar  iron,  as  it  is  general- 
ly formed  into  long  bars.  A  considerable  loss  of  weight  at- 
tends the  process  from  the  dissipation  of  the  foreign  substances 
contained  in  the  crude  iron,  and  from  the  oxidation  of  the  sur- 
face of  the  metal.  The  operation  is  generally  performed  on 
the  varieties  called  white,  or  grey  crude  iron. 

Forging. — Forging  consists  in  changing  the  form  of  iron 
and  other  malleable  metals,  by  percussion  applied  to  them, 
while  they  are  softened  by  heat.  Iron  when  exposed  to  the 
action  of  great  heat,  becomes  highly  malleable  and  ductile.  It 
is  also  capable  of  welding,  at  a  sufficiently  high  temperature. 
Most  other  metals  have  their  malleability  improved  by  a  cer- 
tain degree  of  heat,  but  become  brittle  if  the  heat  is  carried 
near  to  their  fusing  point.  The  strength  and  quality  of  iron, 
on  the  contrary,  are  improved  by  forging  at  a  strong  white 


ARTS  OF  METALLURGY. 


419 


heat,  since  the  parts  become  consolidated,  and  the  flaws  oblit- 
erated, by  hammering  at  a  welding  temperature. 

The  joint  action  of  the  heat  and  current  of  air,  used  in 
forges,  tends  to  oxidate  rapidly  the  surface  of  iron.  The  ox- 
ide which  is  formed  has  some  tendency  to  vitrification  when 
combined  with  siliceous  matter.  Hence  it  is  a  common  prac- 
tice among  workmen,  to  immerse  the  iron  in  sand,  when  it  is 
near  to  a  welding  heat.  A  vitreous  coating  is  by  this  means 
formed,  which  protects  the  surface  of  the  iron  from  further  oxi- 
dation. This  coating  would  prevent  the  different  pieces  from 
uniting  by  welding,  were  it  not  that  its  fluidity  causes  it  to  es- 
cape, while  under  the  action  of  the  hammer. 

The  forging  at  the  furnaces,  of  large  masses  of  iron,  called 
blooms,  is  performed  by  the  aid  of  tilt  hammers,  as  is  also 
that  of  anchors  and  various  other  massive  implements  and 
parts  of  machines.  Bars  of  iron  are  commonly  rolled,  and 
when  heavier  articles,  such  as  anchors,  are  to  be  made,  a  suffi- 
cient number  of  bars  for  the  purpose  are  welded  together. 

A  tilt  hammer  of  the  kind  used  in  iron  works,  is  shown  in 
PI.  IX.  Fig.  2.  A  B  is  the  hammer,  which  turns  upon  the 
fulcrum  C.  At  D  is  a  wheel  or  cylinder  furnished  with  wipers, 
a  6  c,  &£c.  each  of  which  as  it  passes,  strikes  the  end  A  of  the 
helve,  and  causes  the  hammer  end  B  to  rise.  The  hammer 
then  descends  with  its  own  weight,  and  is  accelerated  by  the 
recoil  of  the  end  A,  from  the  fixed  obstacle  E.  The  wipers 
may  be  indefinitely  varied  in  number  and  position,  and  are 
sometimes  applied  on  the  other  side  of  the  fulcrum.  The  re- 
coil hkewise,  is  sometimes  produced  by  a  spring  placed  over 
the  end  B  of  the  hammer.  The  motions  of  these  engines  is 
extremely  rapid,  and  is  commonly  regulated  by  a  fly  wheel. 

Rolling  and  Slitting, — Malleable  iron  is  commonly  wrought 
into  those  shapes  which  have  flat,  parallel  surfaces,  by  submit- 
ting it  to  compression  between  rollers.  Bars,  plates,  and  sheets 
of  iron  are  formed  in  this  way.  A  pair  of  heavy  cylindrical 
rollers,  made  of  iron,  chill  cast,  and  turned  smooth,  are  con- 
nected together  by  strong  iron  bearings,  a  space  being  left  be- 


414 


ARTS  OF  METALLURGY. 


tween  them  equal  to  the  intended  thickness  of  the  metal  which 
is  to  be  rolled.  This  distance  is  varied  by  adjusting  it  with 
powerful  screws.  The  iron  which  is  to  be  rolled,  is  prepared 
by  heating  it  red  hot,  and  in  this  state  it  is  presented  to  the 
rollers.  As  soon  as  any  part  has  entered  so  as  to  fill  the  space 
between  the  rollers,  the  friction,  or  adhesion,  becomes  sufficient 
to  draw  in  the  remainder,  in  opposition  to  the  force  with  which 
the  metal  resists  compression.  The  iron  in  passing  through,  is 
compressed  into  a  uniform  plate  of  equal  thickness,  and  is  at 
the  same  time  extended  in  length,  but  is  very  little  increased 
in  breadth.  As  the  rollers  usually  move  with  considerable  ve- 
locity, the  heated  iron  may  be  passed  several  times  between 
different  pairs  of  rollers,  before  it  cools.  To  prevent  the  rollers 
from  becoming  heated,  a  continual  stream  of  water  is  let  fall 
upon  their  surface. 

As  the  principal  extension,  which  plates  receive,  is  in  a  longi- 
tudinal direction,  it  is  necessary  to  vary  their  position  when  it 
is  desired  to  increase  their  width.  This  is  sometimes  done  by 
passing  them  in  an  oblique  direction,  but  in  making  sheet  iron 
and  wide  plates,  it  is  necessary  to  pass  the  pieces  through  the 
rollers  in  the  direction  of  their  breadth,  as  well  as  length,  that 
they  may  be  extended  in  both  directions.  Very  thin  plates, 
like  those  used  for  tinned  iron,  are  repeatedly  doubled,  and 
passed  between  the  rollers,  so  that  in  the  thinnest  plates  16 
thicknesses  are  rolled  together,  care  being  taken  to  change  their 
relative  positions,  and  to  interpose  oil  to  prevent  them  from  co- 
hering. The  last  rollings  are  performed  while  the  metal  is 
cold.  Bars  which  are  square,  round,  and  of  various  other 
shapes,  are  formed  between  rollers  which  have  grooves  cut 
upon  their  circumferences,  corresponding  in  shape  to  half  the 
bar  to  be  made.  Even  rails  of  malleable  iron,  for  rail  roads, 
have  lately  been  made  between  rollers  formed  for  the  purpose. 
And  at  some  furnaces  where  malleable  iron  is  made,  the  forge 
hammer  is  dispensed  with,  and  reliance  is  placed  on  the  rollers 
alone  to  consolidate  and  equalize  the  masses  of  metal. 


ARTS   OF  METALLURGT. 


415 


Slitting  rollers,  or  those  intended  for  dividing  plates  of  iron 
into  narrow  rods,  are  formed  with  elevated  rings  upon  their 
circumferences,  which  reciprocally  enter  between  each  other, 
their  edges  being  angular  and  passing  in  close  contact  with 
each  other,  so  as  to  cut  like  shears.  These  rings  are  separate- 
ly made,  so  that  they  can  be  removed  from  the  rollers  for  the 
purpose  of  sharpening  them,  when  necessary. 

Wire  Drawing. — ^The  manufacture  of  wire  consists  in  draw- 
ing a  piece  of  metal  through  a  conical  hole,  in  a  steel  plate, 
which  forms  it  into  a  regular  cylindrical  filament.  The  size  of 
this  filament  may  be  reduced,  and  the  length  extended,  indefi- 
nitely, by  passing  it  through  successive  holes,  which  gradually 
diminish  in  diameter. 

To  prepare  the  iron  for  drawing,  it  is  fi:rst  subjected  to  the 
action  of  the  hammer,  till  it  is  reduced  to  a  size,  that  will  admit 
of  its  being  drawn  through  the  plate.  Sometimes  the  iron  is 
prepared  by  rolling,  but  the  best  wire  is  produced  when  the 
metal  has  been  thoroughly  hammered. 

The  rod  of  iron  which  has  been  prepared  in  this  manner  is 
next  drawn  through  one  of  the  larger  holes  in  the  steel  plate. 
Various  machines  are  employed  to  overcome  the  resistance 
which  the  plate  opposes  to  the  compression  and  passage  of  the 
wire.  In  general,  the  end  of  the  wire  is  held  by  pincers,  and 
as  fast  as  the  wire  is  drawn  through  the  plate,  it  is  wound  upon 
a  roller  by  the  action  of  a  wheel  and  axle,  or  other  power. 
Sometimes  a  rack  and  pinion  is  employed  for  this  purpose,  and 
sometimes  a  lever  which  acts  at  intervals,  and  takes  fresh  hold 
of  the  wire  each  time  that  the  force  is  applied. 

The  finer  kinds  of  wire  are  made  from  the  larger  by  repeat- 
ed drawings,  each  of  which  is  performed  through  a  smaller 
hole  than  the  preceding.  As  the  metal  becomes  stiff  and  hard 
by  the  repetition  of  this  process,  it  is  necessary  to  anneal  it 
from  time  to  time,  to  restore  its  ductility.  It  is  also  occasion- 
ally immersed  in  an  acid  liquid,  to  loosen  the  superficial  oxide 
which  is  formed  in  the  process  of  annealing. 


416 


ARTS  OF  METALLURGY. 


JVail  Making. — Nails  are  made  both  by  hand,  and  by  ma- 
chinery. Wrought  nails  are  made  singly  at  the  forge  and  an- 
vil, by  workmen  who  acquire  from  practice  great  despatch  in 
the  operation.  Machines  have  been  made  for  making  these 
nails  perfectly,  and  with  rapidity ;  yet  they  have  not  come  into 
general  use,  owing  to  the  cheapness  of  the  product  by  manual 
labor.  Cut  nails  are  made  almost  wholly  by  machinery,  in- 
vented in  this  country.  The  iron,  after  having  been  rolled 
and  slit  into  rods,  is  flattened  into  plates  of  the  thickness  intend- 
ed for  the  nails,  by  a  second  rolling.  The  end  of  this  plate  is 
then  presented  to  the  nail  machine,  by  a  workman,  who  turns 
the  plate  over  once  for  every  nail.  The  machine  has  a  rapid 
reciprocating  motion,  and  cuts  off  at  every  stroke  a  wedge 
shaped  piece  of  iron,  constituting  a  nail  without  a  head.  This 
is  immediately  caught  near  its  largest  end,  and  compressed  be- 
tween gripes.  At  the  same  time  a  strong  force  is  applied  to  a 
die  at  the  extremity,  which  spreads  the  iron  sufficiently  to  form 
a  head  to  the  nail.  Some  nails  are  made  of  cast  iron,  but 
these  are  always  brittle,  unless  afterwards  converted  into  mal- 
leable iron  by  the  requisite  process. 

Gun  Making. — Cannon,  carronades,  &ic.  whether  of  iron 
or  brass,  are  cast  in  sand,  and  afterwards  bored.  Muskets  and 
fowling  pieces  are  forged  from  bars  of  malleable  iron.  The 
bar  is  first  flattened  by  hammering,  till  it  attains  the  requisite 
width.  It  is  then  made  into  a  tube  by  turning  it  over  a  man- 
drel, or  cylindrical  rod,  of  a  size  which  is  smaller  than  that  of 
the  intended  bore.  The  edges  are  made  to  overlap  each  oth- 
er about  half  an  inch,  and  are  firmly  welded  together.  The 
whole  is  then  consolidated  and  strengthened,  by  hammering  it 
for  some  time  in  semicircular  grooves  on  a  swage,  or  anvil, 
which  is  furrowed  for  the  purpose.  To  render  the  barrel 
smooth  on  the  inside,  and  perfectly  true,  it  is  afterw^ards  bored 
out  with  an  instrument  somewhat  larger  than  the  mandrel,  and 
several  such  instruments  of  different  sizes  are  employed  in 
succession.  The  breech  of  the  barrel  is  closed  by  a  strong 
plug  which  is  firmly  screwed  in  at  the  extremity.    The  pro- 


ARTS   OF  METALLURGY. 


417 


jecting  parts  of  the  barrel,  such  as  the  sight,  and  tlic  loops 
which  confine  it  to  the  stocks,  are  soldered  on.  The  construc- 
tion of  the  lock,  and  other  appendages,  is  readily  understood 
from  inspection. 

Steel. — When  malleable  iron  is  recombined  with  carbon  in 
a  niuch  smaller  proportion,  it  forms  steel.  Different  methods 
are  followed  to  form  this  combination.  The  product  varies 
according  to  the  method  pursued,  and  is  also  affected  by  the 
introduction  of  other  substances  into  the  combination.  The 
best  steel  is  made  from  Swedish  and  Russian  iron. 

The  general  method  of  forming  steel,  is  by  the  process  of 
cementation.  A  furnace  is  constructed  of  a  conical  form,  in 
which  are  two  large  cases,  or  troughs,  of  fire  brick,  capable  of 
holding  some  tons  of  iron.  Beneath  these  is  a  long  grate,  on 
which  the  fuel  is  placed.  On  the  bottom  of  the  case  is  placed  a 
layer  of  charcoal  dust ;  over  this  a  layer  of  bars  of  malleable 
iron  ;  over  this,  again,  a  layer  of  charcoal  powder  ;  and  the 
series  of  alternate  layers  of  charcoal  and  iron,  is  thus  raised 
to  a  considerable  height.  The  whole  is  covered  with  clay  to 
exclude  the  air,  and  flues  are  carried  through  the  pile  from  the 
furnace,  so  as  to  communicate  the  heat  more  completely  and 
equally.  The  fire  is  kept  up  for  eight  or  ten  days.  The 
progress  of  the  cementation  is  discovered  by  w^ithdrawing  a 
bar,  called  the  test  bar,  from  an  aperture  in  the  side.  When 
the  conversion  of  iron  into  steel,  appears  to  be  complete,  the 
fire  is  extinguished,  the  w^hole  is  left  to  cool  for  six  or  eight 
days  longer,  and  is  then  removed. 

The  iron  prepared  in  this  manner,  is  named  blistered  steel, 
from  the  blisters  which  appear  on  its  surface.  To  render  it 
more  perfect,  it  is  subjected  to  the  action  of  the  hammer,  in 
nearly  the  same  manner  which  is  practised  with  forged  iron  ; 
it  is  beat  very  thin,  and  is  thus  rendered  more  firm  in  its  tex- 
ture, and  more  convenient  in  its  form.  In  this  state  it  is  often 
called  tilted  steel.  When  the  bars  are  exposed  to  heat  in  a 
furnace  sufficient  to  soften  them,  and  afterwards  doubled, 
drawn  out,  and  welded,  the  product  is  called  shear  steel.  Cast 
53 


418 


ARTS   OF  METALLURGY. 


steel  is  made  by  fusing  bars  of  common  blistered  steel  with  a 
flux  of  carbonaceous  and  vitreous  substances,  in  a  large  cruci- 
ble, placed  in  a  wind  furnace.  When  the  fusion  is  complete,  it 
is  cast  into  small  bars  or  ingots.  Cast  steel  is  harder  and  more 
elastic,  has  a  closer  texture,  and  receives  a  higher  polish,  than 
common  steel.  It  is  capable  of  still  farther  improvement  by 
being  subjected  to  the  action  of  the  hammer.  ^ 

Steel  is  generally  prepared  from  malleable  iron.  It  can  also 
be  formed  from  crude  cast  iron,  as  in  Mr  Lncas'  method  here- 
after described.  Several  varieties  of  cast  iron  have  been  used 
for  this  purpose.  The  crude  iron  from  certain  ores,  as  the 
sparry  iron  ore,  is  capable  of  this  conversion.  The  steel  thus 
obtained,  is  named  natural  steel,  but  is  inferior  to  that  obtained 
by  cementation. 

Alloys  of  Steel. — Messrs  Stodart  and  Faraday,  have  succeed- 
ed in  making  some  useful  alloys  of  steel  with  other  metals,  f 
Their  experiments  induced  them  to  believe  that  the  celebrated 
Indian  steel  called  ivootz,  is  an  alloy  of  steel  with  small  quanti- 
ties of  silicium  and  aluminum  ;  and  they  succeeded  in  preparing 
a  similar  compound,  possessed  of  all  the  properties  of  wootz. 
They  ascertained  that  silver  combines  with  steel,  forming  an 
alloy,  which,  although  it  contains  only  1 -500th  of  its  weight  of 
silver,  is  superior  to  wootz,  or  to  the  best  cast  steel  in  hardness. 
The  alloy  of  steel  with  100th  part  of  platinum,  though  less 
hard  than  that  with  silver,  possesses  a  greater  degree  of  tough- 
ness, and  is  therefore  highly  valuable  when  tenacity  as  well  as 
hardness  is  required.  The  alloy  of  steel  whh  rhodium  even 
exceeds  the  two  former  in  hardness.  '  The  compound  of  steel 
with  palladium,  and  of  steel  with  iridium  and  osmium,  is  like- 
wise exceedingly  hard  ;  but  these  alloys  cannot  be  applied  to 

*  Writers  difler  in  regard  to  the  proportion  of  carbon  contained  in  cast  steel. 
Mr  Buttery,  in  lire's  Dictionary,  states  that  the  amount  is  less  than  in  common 
steel,  and  that  no  charcoal  is  added  in  making  it.  He  also  states  that  it  does 
not  melt  at  a  welding  temperature,  but  falls  to  pieces  like  sand,  under  the 
hammer,  and  the  parts  refuse  to  become  again  united. 

f  Philosophical  Transactions,  for  J82r?. 


ARTS   OF  METALLURGY. 


419 


useful  purposes,  owing  to  the  rarity  of  the  metals  of  which  they 
are  composed.  M.  Berthier  has  also  produced  a  useful  alloy 
by  combining  with  the  steel  a  small  portion  of  chromium. 

Case  Hardening. — The  process  of  case  hardening  consists 
in  converting  the  surface  of  iron  into  steel,  and  is  used  for  giv- 
ing a  superficial  hardness  to  various  instruments.  It  is  effected 
by  inclosing  the  article  which  is  to  be  case  hardened,  in  a  box 
with  some  carbonaceous  substance,  usually  animal  charcoal, 
and  exposing  it  to  heat,  until  the  surface  is  converted  into  steel. 
The  same  term  is  sometimes  improperly  applied  to  the  method 
of  chill  casting,  which  has  been  already  mentioned. 

Tempering. — The  most  remarkable,  as  well  as  the  most  useful ' 
of  the  properties  of  steel,  is  the  power  which  it  has  of  changing 
permanently  its  degree  of  hardness,  by  undergoing  certain 
changes  of  temperature.  No  other  metal,  says  Thenard,  is 
known  to  possess  this  property,  and  iron  itself  acquires  it  only 
when  it  is  combined  with  a  minute  portion  of  carbon.  If  steel 
is  heated  to  redness,  and  suddenly  plunged  in  cold  water,  it  is 
found  to  become  extremely  hard,  but  at  the  same  time,  it  is  too 
brittle  for  use.  On  the  other  hand  if  it  be  suffered  to  cool  very 
gradually,  it  becomes  more  soft,  and  ductile,  but  is  deficient  in 
strength.  The  process  of  tempering  is  intended  to  give  to 
steel  instruments  a  quality  intermediate  between  brittleness  and 
ductility,  which  shall  insure  them  the  proper  degree  of  strength 
under  the  uses  to  which  they  are  exposed.  For  this  purpose, 
after  the  steel  has  been  sufficiently  hardened,  it  is  partially 
softened,  or  let  down  to  the  proper  temper,  by  heating  it  again 
in  a  less  degree,  or  to  a  particular  temperature,  suited  to  the 
degree  of  hardness  required ;  after  which  it  is  again  plunged 
in  cold  water. 

Different  methods  have  been  pursued,  for  determining  the 
temperature  proper  for  giving  the  requisite  temper  to  different 
instruments.  One  method  is  to  observ^e  the  shades  of  color 
which  appear  on  the  surface  of  the  steel,  and  succeed  each 
other  as  the  temperature  increases.  Thus  at  430  degrees  of 
Fahrenheit,  the  color  is  pale,  and  but  slightly  inclining  to  yellow. 


420 


ARTS   OF  METALLURGY. 


This  is  the  temperature  at  which  lancets  are  tempered.  At 
450  degrees,  a  pale  straw  color  appears,  which  is  found  suita- 
ble for  the  best  razors  and  surgical  instruments.  At  470  de- 
grees a  full  yellow  is  produced,  suitable  for  penknives,  com- 
mon razors,  he.  At  490  degrees,  a  brown  color  appears, 
which  is  used  to  temper  shears,  scissors,  garden  hoes,  and 
chisels  intended  for  cutting  cold  iron.  At  510  degrees  the 
brown  becomes  dappled  with  purple  spots,  which  shows  the 
proper  heat  for  tempering  axes,  common  chisels,  plane  irons, 
&c.  At  530  degrees  a  purple  color  is  established,  and  at  this 
degree  the  temper  is  given  to  table  knives  and  large  shears. 
At  550  degrees,  a  bright  blue  appears,  used  for  swords  and 
watch  springs.  At  560  degrees  the  color  is  a  full  blue,  and  is 
used  for  fine  saws,  augers,  &;c.  At  600  degrees  a  dark  blue 
approaching  to  black,  has  become  settled,  and  is  attended  with 
the  softest  of  all  the  grades  of  temper,  used  only  for  the  larger 
kinds  of  saws. 

Another  method  of  giving  the  requisite  temper  has  been 
practised  upon  various  articles.  The  pieces  of  steel  are  cov- 
ered with  oil  or  tallow,  or  put  into  a  vessel  containing  either  of 
these  ingredients,  and  heated  over  a  moderate  fire.  The  ap- 
pearance of  the  smoke  from  the  oil  or  tallow,  indicates  the  de- 
gree of  heat.  If  the  smoke  just  appear,  the  temper  corres- 
ponds with  that  indicated  by  the  straw  color  when  the  metal  is 
heated  alone.  If  so  much  heat  is  applied  that  a  black  smoke 
arises,  this  points  out  a  different  degree  of  hardness ;  and  so  on, 
till  the  vapor  catches  flame.  By  this  method  a  number  of  pieces 
may  be  done  at  once,  with  comparatively  little  trouble,  and  the 
heat  is  also  more  equally  applied. 

A  still  more  accurate  method  of  producing  any  desired  de- 
gree of  temper,  is  to  immerse  the  steel  in  some  fluid  medium, 
the  temperature  of  which  is  kept  regulated  by  the  thermome- 
ter. Thus  oil,  which  boils  at  about  600  degrees,  may  be  used 
for  this  purpose  at  any  degree  of  heat  which  is  below  that 
number  of  degrees.  Mr  Parkes  has  recommended  the  em- 
ployment of  metallic  batiis,  chiefly  composed  of  lead  and  tin, 


ARTS   OF  METALLURGY. 


431 


in  different  proportions,  which  pass  into  fusion  at  definite  tem- 
peratures, and  which  can  be  used  for  tempering  steel,  as  soon 
as  they  arrive  at  their  melting  points.  ^  f 


*  The  following  table  of  metallic  baths  is  given  in  Parkes'  Chemical  Essays, 
Appendix  to  vol.  il. 


No. 

Edge  Tools  to  be  tempered  in  the  various 

Composition 

Temper. 

133.ths* 

i>i  me  jDatn . 

F&hren. 

1 

Lancets,  in  a  Bath  composed  of 

7   lead  4  tin 

420^ 

2 

Other  surgical  instruments 

7i  lead  4  tin 

430 

3 

Razors,  &c. 

8  lead  4  tin 

442 

4 

Penknives  and  some  implements  of 

surgery 

Si  lead  4  tin 

450 

5 

Larger  penknives,  scalpels,  &c. 

10   lead  4  tin 

470 

6 

Scissors,  shears,  garden  hoes,  cold 

chisels,  &c. 

14   lead  4  tin 

490 

7 

Axes,  firmer  chisels,  plane  irons, 

pocket  knives,  &c. 

19  lead  4  tin 

509 

8 

Table  knives,  large  shears,  &c. 

30  lead  4  tin 

530 

9 

Swords,  watch  springs,  &c. 

48  lead  4  tin 

550 

10 

Large  springs,  daggers,  augers,  small 

fine  saws,  &c 

50  lead  2  tin 

558 

11 

Pit  saws,  hand  saws,  and  some  par- 

ticular springs 

Boiling  linseed  oil 

600 

12 

Articles  which  require  to  be  still 

somewhat  softer 

Melting  lead 

612 

t  Formerly,  no  man  in  Great  Britain  knew  how  to  temper  a  sword  in  such  a 
way  that  it  would  bend  for  the  point  to  touch  the  heel  and  spring  back  again 
uninjured,  except  one  Andrew  Ferrara,  who  resided  in  the  Highlands  of 
Scotland.  The  demand  which  this  man  had  for  his  swords  was  so  great,  that 
he  employed  workmen  to  forge  them,  and  spent  all  his  own  time  in  tempering 
them ;  and  found  it  necessary,  even  in  the  day  time,  to  work  in  a  dark  cellar, 
that  he  might  be  better  able  to  observe  the  progress  of  the  heat,  and  that  the 
darkness  of  his  workshop  might  favor  him  in  the  nicety  of  the  operation. 

The  swords  which  were  formerly  in  the  highest  repute,  were  made  at 
Damascus  in  Syria.  The  method  by  which  these  were  made,  has  long  been 
lost,  or  perhaps  it  was  never  thoroughly  known  to  Europeans  ;  but  from  their 
striated  appearance,  it  has  been  supposed  that  they  were  formed  by  alternate 
layers  of  extremely  thin  plates  of  iron  and  steel,  bound  together  with  iron 
wire,  and  then  firmly  cemented  together  by  welding.  These  weapons  never 
broke,  even  in  the  hardest  conflict,  and  retained  so  powerful  an  edge,  as  to  be 
capable  of  cutting  through  armour.  Various  other  explanations  have  been 
given  in  regard  to  the  character  and  structure  of  the  Damascus,  or  damasked, 
steel. 


4231 


ARTS   OF  METALLURGY. 


Cutlery. — Under  the  head  of  cutlery,  are  comprehended 
numerous  instruments,  designed  for  cutting  or  penetration,  and 
which  are  made  of  steel,  mostly  by  the  processes  of  forging, 
tempering,  grinding,  and  polishing.  The  inferior  kinds  of 
cutlery  are  made  of  blistered  steel  welded  to  iron.  Tools  of 
a  better  quality  are  manufactured  from  shear  steel,  while  the 
sharpest  and  most  delicate  instruments,  are  formed  of  cast  steel. 

The  first  part  of  the  process  consists  in  forging,  and  is  varied 
according  to  the  kind  of  article  to  be  formed.  Common  table 
knives,  have  the  blade  forged  of  steel,  and  welded  to  a  piece 
of  iron,  out  of  which  the  shoulder,  and  part  which  enters  the 
handle,  are  made,  the  shape  being  given  to  them  by  hammering 
in  a  die  and  swage.  They  are  afterwards  tempered  and 
ground.  Forks  are  made  by  forging  the  shank,  and  flattening 
the  other  end  to  the  length  intended  for  the  prongs.  The 
prongs  are  made  by  stamping  the  metal  at  a  white  heat,  be- 
tween two  dies,  the  uppermost  of  which  is  attached  to  a  heavy 
weight,  and  falls  from  a  height.  The  shape  is  thus  given  to 
the  fork,  leaving,  however,  a  flat  thin  piece  of  metal  between 
the  prongs,  w^hich  is  afterwards  cut  out  with  a  fly  press.  They 
are  subsequently  filed,  bent,  hardened,  and  polished. 

Blades  of  penknives  are  forged  from  the  end  of  a  rod  of 
steel,  and  cut  off*,  together  with  metal  enough  to  form  the  joint. 
The  small  recess  in  which  the  nail  is  inserted  to  open  the 
knife,  is  made  with  a  curved  chisel,  while  the  steel  is  hot. 
Razors  are  forged  from  cast  steel,  much  in  the  same  manner 
as  knives.  The  anvil  is  commonly  a  little  rounded  at  the 
sides,  for  the  purpose  of  making  the  sides  of  the  razor  a  little 
concave,  and  the  edge  thinner.  In  forging  scissors,  the  shape 
is  given  to  the  different  parts,  by  hammering  them  upon  differ- 
ent indented  surfaces,  called  bosses.  The  bows,  which  receive 
the  finger  and  thumb,  are  made  by  punching  a  hole  in  the 
metal,  and  enlarging  it  by  hammering  it  round  a  tool,  called  a 
beak  iron.  The  halves  are  finished  by  filing  and  grinding,  and 
afterwards  united  by  a  joint.  Saws  are  made  from  steel  plates 
rolled  for  the  purpose,  and  have  their  teeth  cut,  and  finished 


ARTS   OF  METALLURGY. 


423 


by  filing,  and  set  by  a  suitable  instrument.  Axes,  adzes,  and 
other  large  tools,  are  forged  from  iron,  and  have  a  steel  piece 
welded  on,  of  the  proper  size  to  form  the  edge. 

To  enable  the  steel  to  be  wrought,  it  is  brought  to  its  softest 
state,  but  after  the  shape  is  given  to  the  instrument,  the  steel  is 
hardened  and  tempered  by  the  methods  already  described. 
The  remaining  part  of  the  manufacture  consists  in  grinding, 
polishing,  and  setting  the  instrument,  to  produce  a  smooth  sur- 
face and  a  sharp  edge.    The  grinding  is  performed  upon  stones 
of  various  kinds,  among  which  freestone  is  perhaps  the  most 
common.    These  stones  are  made  to  revolve  by  machinery, 
and  move  with  prodigious  velocity,  so  that  the  surface,  in  some 
cases,  passes  over  six  or  seven  hundred  feet  in  a  second,  and 
stones  have  been  burst  by  their  own  centrifugal  force.  For 
grinding  flat  surfaces,  like  those  of  saws,  the  largest  stones  are 
used;  while  for  concave  surfaces,  like  the  sides  of  razors, smaller 
stones  are  used  on  account  of  their  greater  convexity.  The 
internal  surfaces  of  scissors,  forks,  Sic.  which  cannot  be  applied 
to  the  stone,  are  ground  with  sand  and  emery,  applied  with  in- 
struments of  wood,  leather,  and  other  elastic  substances.  The 
last  polish  is  given  by  the  impure  oxide  of  iron,  called  colcothar, 
crocus,  and  by  the  French  Rouge  J'  Angleterre.    The  edges 
are  lastly  set  with  hones  and  whetstones,  according  to  the 
degree  of  keenness  required.    The  test  used  by  cutlers  for 
determining  the  goodness  of  the  edge  and  point  of  a  lancet,  is, 
that  it  shall  pass  through  a  piece  of  soft  leather  without  sensible 
resistance.    JSeedles  are  polished  by  tying  them  in  large  bun- 
dles with  emery  and  oil,  and  rolling  them  under  a  heavy  plank 
till  they  become  smooth  by  mutual  attrition.    The  shape  is 
previously  given,  and  the  eye  made  with  a  steel  punch. 

A  process  has  been  invented  by  Mr  Lucas,  for  converting 
edge  tools,  nails,  &jc.,  made  of  cast  iron,  into  good  steel.  It 
consists  in  stratifying  the  cast  articles,  in  cylindrical  metallic 
vessels,  with  native  oxide  of  iron,  and  then  submitting  the 
whole  to  a  regular  heat  in  a  furnace  built  for  the  purpose,  ft 
is  not,  however,  necessary  that  the  oxide  employed  should  be 
a  native  oxide,  any  artificial  oxide  being  equally  effectual. 


424 


ARTS   OF  METALLURGY. 


The  cast  iron,  of  which  this  cutlery  is  made,  is  brittle  in  the 
first  instance,  like  other  cast  iron,  in  consequence  of  the  carbon 
contained  in  it ;  but  the  great  heat  which  it  undergoes,  aided 
by  the  pulverized  oxide,  separates  a  part  of  the  carbon.  This 
uniting  with  the  oxygen  of  the  ground  oxide  of  iron,  is  dissipated 
in  the  state  either  of  carbonic  oxide,  or  carbonic  acid  gas,  and 
the  articles  are  then  converted  into  a  state  nearly  similar  to  that 
of  good  cast  steel  cutlery.  They  do  not,  however,  receive 
so  fine  an  edge,  and  do  not  bear  hardening  and  tempering  in 
the  common  manner. 


Murray's  System  of  Chemistry,  4  vols,  8vo.  1806; — Parkes's 
Chemical  Essays,  2  vols,  Svo.  1823; — Gray's  Operative  Chemist,  8vo. 
1828; — Dumas,  TraiU^de  Chimie  Appliquie  aux  Arts,  &c.  4  torn.  Svo. 
1828-9 ; — FouRCROY,  Systeme  des  Connaissances  ChimiqueSy  11  torn. 
1801 ; — Aiken's  Dictionary  of  Chemistry  and  Mineralogy,  2  vols,  4to. 
1807  ; — Martin's  Circle  of  Mechanic  Arts,  4to.  1818  ; — Emporium  of 
Arts  and  Sciences,  Philadelphia,  1812-14 ; — Franklin  Journal,  Phila- 
delphia, 1826,  and  after  ; — Rees's  Cyclopedia,  various  heads  ; — 
Ure's  Dictionary  of  Chemistry; — Thenard,  Traitede  C/imte,5tom. 
Svo.  1824; — Works  of  Bergman,  Klaproth,  Lewis,  &c. 


CHAPTER  XVIII. 


ARTS  OF  COMMUNICATING  AND  MODIFYING  COLOR. 

An  extensive  branch  of  industry  has  for  its  object  the  effect- 
ing of  changes  in  the  natural  colors  of  bodies.  The  artificial 
modifications,  produced  in  color,  may  be  either  jnechanical  and 
superficial,  or  chemical  and  intrinsic.  In  painting,  gilding,  and 
similar  processes,  the  original  color  of  a  substance  is  not  alter- 
ed, but  it  is  mechanically  concealed  by  another  substance  which 
covers  it  from  view.  On  the  other  hand,  in  bleaching  and 
dyeing,  the  color  of  the  whole  substance  is  intrinsically  chang- 
ed, by  a  chemical  action.  This  difference  of  character  has 
given  rise  to  distinct  arts  in  coloring,  the  processes  of  which 
are  for  the  most  part  dissimilar. 

OF  APPLYING  SUJPERFICIAL  COLOR. 

Painting. — Common  painting,  when  disconnected  with  de- 
sign, has  for  its  object  to  produce  a  uniform  and  permanent  coat- 
ing upon  surfaces,  by  applying  to  them  a  compound,  which  is 
more  or  less  opaque.  In  many  cases  painting  is  applied  only 
for  ornament,  but  it  is  more  frequently  employed  to  protect 
perishable  substances  from  the  changes  to  which  they  are  liable 
when  exposed  to  the  atmosphere,  and  other  decomposing 
agents.  The  effect  and  durability  of  different  coverings  em- 
ployed in  this  way,  depends  upon  the  kind  of  pigment  used, 
and  still  more  upon  the  vehicle,  or  uniting  medium,  by  the  in- 
tervention of  which  it  is  applied. 

Colors. — The  coloring  substances,  employed  by  painters, 
comprise  a  great  variety  of  articles  derived  from  the  mineral, 
vegetable,  and  animal  kingdoms.  They  are  employed  in  a 
54 


426 


ARTS   OF  COMMUNICATING 


State  of  minute  subdivision,  and  commonly  mixed  with  a  fluid 
which  is  more  or  less  viscid  and  tenacious.  When  applied 
upon  the  surface  of  canvass,  wood,  or  other  bodies,  they  com- 
municate their  color,  by  covering  and  concealing  the  original 
color  of  the  surface,  while  they  substitute  their  own  in  stead. 
Those  which  are  perfectly  opaque,  are  called  body  colors,  such 
as  white  lead,  and  vermilion ;  while  those  which  are  partially 
pellucid,  are  called  transparent  colors,  as  prussian  blue,  terra 
di  sienna,  and  lake.  Transparent  colors  do  not  wholly  conceal 
the  colors  beneath  them,  but  produce  the  combined  effect  of 
the  two.  The  process  called  by  painters  glazing,  consists  in 
laying  a  transparent  color  over  one  of  a  different  tint.  Trans- 
parent colors  are  sometimes  mixed  with  a  white  earth  to  give 
them  a  body,  where  it  is  necessary  to  cover  entirely  the  pre- 
vious surface.  Common  whiting  is  usually  employed  for  this 
purpose. 

The  following  list  comprises  the  principal  coloring  substan- 
ces, used  as  paints,  exclusive  of  those  which  belong  only 
to  the  art  of  dyeing. 

Blues. —  Ultramarine  is  the  richest  and  most  durable  of  all  the  blues. 
It  is  not  altered  by  time,  and  bears  exposure  to  a  red  heat  without 
changing  its  color.  It  is  made  only  from  the  lapis  lazuli,  a  stone 
brought  from  several  parts  of  Asia,  which  bears  an  extremely  high 
price. 

Prussian  blue  is  a  strong  and  durable  color.  In  the  present  language 
of  chemistry,  it  is  a  ferrocyanate  of  the  peroxide  of  iron.  It  is  made 
from  blood,  and  other  animal  matters,  dried  and  heated  to  redness  with 
an  equal  weight  of  pearl  ash.  The  residue,  which  consists  chiefly  of 
cyanuret  of  potassium,  and  carbonate  of  potass,  is  dissolved  in  water, 
and  after  being  filtered,  is  mixed  with  a  solution  of  alum  and  proto- 
sulphate  of  iron.  A  greenish  precipitate  ensues,  which,  by  exposure 
to  the  atmosphere,  passes  through  different  shades,  till  it  arrives  at  a 
fine  blue  color. 

Blue  verditer  is  a  nitrate  of  copper  combined  with  hydrate  of  lime. 
It  is  made  by  adding  quicklime  to  a  solution  of  copper  in  nitric  acid, 
and  mixing  the  precipitate  with  a  small  portion  more  of  lime.  It  is  a 
full  blue,  much  used  in  paper  staining,  but  is  liable  to  grow  dull. 


AND  MODIFYING  COLOR. 


427 


Smalt  is  a  powdered  glass,  wliich  derives  its  blue  color  from  the 
oxide  of  cobalt.  It  is  chiefly  used  by  strewing  it  on  a  ground  of  some 
other  color. 

Bice  consists  of  smalt  finely  levigated.  It  is  rather  lighter,  and 
very  durable,  but  not  extensively  used. 

Indigo  is  the  deepest  of  all  the  blues  in  common  use.  It  is  very 
durable,  but  more  used  in  dyeing  (which  see)  than  in  painting.  Stone 
blue.  Fig  blue,  (Queen's  blue,  Slc,  consist  of  indigo  reduced  by  starch. 

Reds. —  Vermilion  is  a  bisulphuret  of  mercury,  formed  by  fusing 
sulphur  with  about  six  times  its  weight  of  mercury,  and  subliming  in 
close  vessels.  The  product  is  called  cinnabar,  and  when  powdered, 
vermilion.    It  is  of  a  bright  scarlet  color,  and  stands  tolerably  well. 

ReAl  lead,  otherwise  called  minium,  is  a  deutoxide  of  lead,  formed  by 
exposing  lead,  or  litharge,  to  heat  in  a  furnace,  in  open  vessels,  with  a 
current  of  air  passing  over  it.  The  metal  is  gradually  converted  into 
an  oxide  of  a  bright  orange  red.  Red  lead  is  extensively  consumed 
in  the  manufacture  of  flint  glass.  As  a  pigment,  it  is  brilliant  at  first, 
but  liable  in  time  to  turn  black. 

Chrome  red  is  a  fine  scarlet,  formed  by  boiling  carbonate  of  lead 
with  an  excess  of  chromate  of  potass.  By  Dulong's  method,  67  parts 
of  white  lead  are  boiled  with  82  parts  of  chrome  yellow,  in  water. 

Colcothar,  also  called  crocus  mariis,  and  rouge  angleterre,  is  an  im- 
pure brown  red  oxide  of  iron  which  remains  after  the  distillation  of 
the  acid  from  sulphate  of  iron.  It  forms  a  durable  color,  but  is  most 
used  by  artists  in  polishing  glass  and  metals. 

Ochres. — The  ochres  are  various  earths  containing  iron  in  a  greater 
or  less  degree  of  oxidation.  Venetian  red  is  a  coarse  ochre  of  a  dark 
red  color.  Indian  red  is  an  ochre  brought  from  the  East  Indies,  and 
has  a  shade  inclining  to  purple.  Red  ochre  is  formed  from  yellow  ochre 
by  exposing  it  to  heat.  Burnt  sienna  is  made  from  the  raw  terra 
di  sienna  by  exposure  to  heat,  by  which  process  its  color  is  changed 
from  yellow  to  red.  Bole  is  a  fine  clay,  colored  by  oxide  of  iron,  of 
which  there  are  many  varieties,  from  yellowish  red  to  brown. 

Carmine,  the  most  beautiful  of  all  the  reds,  is  an  animal  substance 
made  from  the  cochineal  insect,  or  coccus  cacti.  It  is  deposited  from 
a  decoction  of  powdered  cochineal  in  water,  to  which  alum,  carbonate 
of  soda,  or  oxide  of  tin  is  added  ;  but  the  preparation  of  the  finest  va- 
rieties is  kept  secret  by  the  manufacturers,  and  probably  depends  much 
upon  the  delicacy  of  the  manipulations.  A  fine  color  is  said  to  be 
made  by  adding  acetic  acid  to  a  solution  of  carmine  in  ammonia. 

Lakes  of  various  shades  are  formed  from  cochineal  precipitated  by 
salts  of  tin,  and  other  agents.  Beautiful  lakes  are  also  prepared  from 
madder,  by  a  process  of  Sir  H.  Englefield,  in  which  the  coloring  sub- 


428  ARTS  OF  COMMUNICATING 

stance  is  precipitated  from  an  infusion  of  madder,  by  adding  solutions 
of  alum,  and  carbonate  of  potass.  The  lake  called  rose  pinky  is  an 
extract  of  Brazil  wood,  mixed  with  whiting  and  alum. 

Rouge  is  made  from  the  flowers  of  the  Carthamus  tindorius  or 
Dyer's  saffron,  also  called  safflower  ;  by  dissolving  an  alkali  in  the  in- 
fusion, and  precipitating  the  coloring  matter  by  lemon  juice.  It  is 
very  fugacious.    Under  the  same  name  other  pigments  are  also  used. 

Yellows. —  Gamboge  is  the  concrete  juice  of  a  tree  growing  in  the 
East  Indies,  [Stalagmitis  camhogioides.)  It  is  externally  of  a  dull 
orange  color,  but  becomes  of  a  bright  yellow,  when  wet,  or  thinly 
spread  upon  a  white  surface.  It  is  partially  soluble  in  water  and  alco- 
hol, and  is  chiefly  used  in  water  colors. 

Orpiment  is  a  sulphuret  (sesquisulphuret)  of  arsenic.  Tiie  paint 
called  kings  yellow,  is  made  from  this  substance,  or  from  its  constitu- 
ents. It  is  a  brilliant,  but  not  very  durable  color,  and  its  use  is  in 
some  cases  dangerous  to  the  health. 

JVaples  yellow  is  prepared  by  exposing  lead  and  antimony  with  po- 
tass, to  the  heat  of  a  reverberatory  furnace.  It  stands  tolerably  well, 
but  turns  black  upon  the  contact  of  iron.  A  native  pigment  of  this 
kind  is  also  obtained  from  a  species  of  lava. 

Yellow  ochre  is  a  native  earth,  the  finer  particles  of  which,  are  sepa- 
rated by  washing,  as  in  similar  substances.  Although  not  very  bright, 
its  cheapness  and  durability  have  caused  it  to  be  extensively  used. 

Terra  di  sienna  is  also  an  ochre,  of  a  deeper  and  brighter  yellow, 
than  most  of  the  others. 

Massicot,  or  masticot,  is  the  protoxide  of  lead,  prepared  by  collecting 
the  gray  film  which  floats  upon  the  surface  of  melted  lead,  and  ex- 
posing it  to  heat  and  air  until  it  assumes  a  yellow  color. 

Chrome  yellow  is  a  chromate  of  lead.  It  is  precipitated  by  adding 
chromate  of  potass  in  solution,  to  a  solution  of  nitrate,  or  acetate,  of 
lead.  It  forms  one  of  the  most  brilliant  yellows,  and  is  extensively 
manufactured  in  this  country,  from  the  chromate  of  iron  found  near 
Baltimore. 

Turpeth  mineral  is  a  subsulphate  of  mercury,  or  rather  a  sub-bisul- 
phate.    It  is  a  pale  yellow,  and  moderately  durable. 

Patent  mineral  yellow  is  a  fused  muriate  of  lead,  made  by  decompos- 
ing common  salt  by  means  of  litharge,  triturating  the  product  with 
water,  washing  away  the  soda,  and  drying  and  fusing  the  muriate. 

Dutch  pink  is  a  cheap  color  used  by  paper  stainers,  composed  of 
whiting  colored  by  a  decoction  of  dyers  wood,  quercitron,  or  French 
berries,  with  alum. 

Greens. —  Verdigris  is  an  acetate  of  copper,  or  strictly,  an  impure 
acetate  of  the  peroxide  of  copper-    It  is  manufactured  in  the  south  of 


AND  MODIFYING  COLOR. 


429 


France  by  covering  plates  of  copper  with  the  refuse  of  the  grapes 
after  making  wine.  It  may  also  be  formed  by  exposing  copper  to  the 
vapor  of  vinegar. 

Terra  verte  is  a  native  blue-green  ochre.  It  is  semitransparent  and 
durable,  but  not  very  bright. 

Brunsimck  green,  called  also  mineraZ  green,  is  an  ammoniaco-muriate 
of  copper,  much  used  for  paper  hangings,  and  occasionally  in  oil 
painting. 

Sap  green  is  the  inspissated  juice  of  the  berries  of  the  buckthorn, 
{Rhamnus  caiharticus.)  It  is  semitransparent,  and  chiefly  used  in 
water  colors. 

Many  of  the  greens  in  common  use  are  compound  colors,  made  by 
the  admixture  of  blue  with  yellow. 

Browns. —  Umber  is  a  light  brov/n  ochre.  Burnt  umber  is  the  same 
substance,  having  its  color  darkened  by  exposure  to  heat.  It  is  dura- 
ble in  both  states. 

Spanish  brown  is  a  coarse  durable  ochre,  its  color  inclining  to  red. 

Bistre  is  prepared  from  common  soot  of  wood,  by  pulverizing  and 
washing.    The  soot  of  the  beech  is  said  to  afford  the  best. 

Asphaltum  is  prepared  from  the  bituminous  substance  of  that  name. 
When  dissolved  in  oil  of  turpentine,  it  is  semitransparent,  and  is  used 
as  a  glaze. 

Ox  gall  consists  of  the  biliary  concretions  found  in  the  gall  bladder 
of  cattle.  It  is  not  soluble  in  water  or  alcohol,  but  dissolves  readily  in 
a  solution  of  potass.  It  is  of  a  yellowish  brown,  and  is  much  valued 
for  the  brightness  and  permanence  of  its  tint.  The  liquid  ox  gall  is 
used  by  painters  to  facilitate  the  laying  on  of  colors. 

Blacks. — Lamp  black  is  a  light  carbonaceous  substance,  thrown  off 
during  the  combustion  of  resinous  and  oily  substances.  The  chips  of 
iir  and  pine  trees  are  burnt  under  tents,  to  the  inside  of  which  the 
lamp  black  adheres. 

Frankfort  black.  This  is  a  charcoal  made  from  the  lees  of  wine.  It 
is  used  in  the  ink  of  copper  plate  printers. 

Ivory  black,  called  also  Cologne  black,  is  made  from  the  shavings 
and  dust  of  ivory,  heated  in  covered  iron  pots.  Various  other  carbo- 
jiaceous  colors  are  made  from  cork,  vine  tAvigs,  peachstones,  &c.,  con- 
verted into  charcoal. 

Indian  ink  is  said  to  be  made  from  different  sorts  of  lamp  black, 
mixed  with  water  and  glue.  The  black  is  obtained  from  the  smoke  of 
oil,  of  fir  wood,  or  of  horse  chesnuts.  A  solution  of  lac  with  borax, 
in  water,  is  said  to  be  the  vehicle  of  the  lamp  black  in  some  kinds. 

Sepia  is  the  black  liquid  obtained  from  the  cuttle  fish.  It  is  of  a 
viscid  consistence,  and  is  preserved  by  drying  it  upon  saucers  or  shells. 


430 


ARTS   OP  COMMUNICATING 


Whites. — fVhite  lead,  formerly  ceruse,  is  a  carbonate  of  lead,  pre- 
pared by  exposing  coils  of  sheet  lead,  in  earthen  pots,  to  the  vapor  of 
vinegar  for  several  weeks.  It  is  sometimes  also  formed  by  precipita- 
tion w^ith  carbonic  acid  from  a  solution  of  acetate  of  lead  in  water. 

Flake  white  consists  of  the  densest  and  thickest  scales,  which  are 
separated  in  making  the  foregoing  article  from  sheet  lead.  It  is  very 
pure,  whereas  the  white  lead  of  commerce  is  adulterated  with  chalk. 

Pearl  white  is  the  subnitrate  of  bismuth,  formerly  called  magistery 
of  bismuth,  precipitated  by  water  from  its  solution  in  nitric  acid.  It 
has  been  used  as  a  cosmetic,  but  grows  yellow  by  age  and  light. 

Whiting. — Common  chalk  separated  in  the  form  of  an  impalpable 
powder  by  washing.    Blanc  de  Troyes  is  similar  to  whiting. 

Zinc  white  is  the  oxide  of  zinc.  It  does  not  work  easily,  but  is 
thought  very  durable.  Various  marls  and  clays  from  Bougival,  Rouen, 
Moudon,  &c.,  are  used  for  white  pigments. 

Preparation. — Coloring  substances,  before  being  used  in 
painting,  require  to  be  reduced  to  a  state  of  extreme  fineness. 
For  this  purpose  they  are  ground  in  a  color  mill,  and  levi- 
gated with  a  stone  and  muller.  In  many  cases  colors  which 
are  insoluble  in  water,  are  separated  by  washing,  the  water 
being  first  made  turbid  with  the  coloring  substance,  and  left 
to  stand  a  short  time,  till  the  coarser  particles  have  subsided. 
The  upper  part  of  the  fluid  with  the  finer  particles  in  suspen- 
sion is  then  poured  off,  and  the  second  deposit  which 
takes  place  from  this  is  sufficiently  fine  for  mixing.  When  a 
greater  degree  of  tenuity  is  required,  the  washing  is  repeated. 

Application. —  As  colors  are  first  prepared  for  use  by  simply 
reducing  them  to  powder,  it  is  necessary  that  some  tenacious 
fluid  should  be  introduced  to  make  their  particles  adhere  to  the 
surface  on  which  they  are  spread.  To  effect  this  end  various 
fluids  are  employed,  and  the  difference  of  the  material  used, 
with  the  method  of  employing  it,  has  given  rise  to  the  modes 
of  painting  in  water,  in  oil,  in  fresco,  in  distemper,  &lc. 

Crayons. — The  most  simple  mode  of  applying  colors  is  by 
the  use  of  crayons.  Crayons  are  cylinders,  or  sticks  of  dry 
colors,  cemented  into  a  friable  mass  like  chalk,  by  the  assist- 
ance of  gum  or  size,  and  sometimes  of  clay.    They  are  used 


AND  MODIFYING  COLOR. 


by  simply  rubbing  them  upon  paper,  and  afterwards  blending 
and  softening  the  shades  by  means  of  a  stump,  or  small  roll  of 
leather,  or  paper.  But  drawings  in  crayons  and  chalks,  have 
always  the  disadvantage  that  they  do  not  adhere  to  the  paper, 
but  are  rubbed  off,  and  defaced,  with  the  slightest  attrition.  In 
this  state  they  can  be  safely  kept  and  examined  only  in  frames 
under  glass.  Various  modes  have  been  practised  for  fixing 
crayon  drawings  upon  paper,  so  as  not  to  be  liable  to  deface- 
ment. Among  other  means,  this  end  may  be  effected  by 
brushing  the  back  of  the  paper  with  a  strong  solution  of  isin- 
glass, or  by  passing  the  drawing  through  a  powerful  press,  in 
contact  with  a  moist  paper. 

Water  Colors. — The  most  common  mode  of  painting  on 
paper,  is  by  the  use  of  water  colors.  These  are  formed  into 
hard  cakes  or  lozenges  with  a  larger  quantity  of  gum,  than  is 
employed  for  crayons.  When  used,  they  are  rubbed  down 
with  water  upon  glass,  or  a  glazed  surface,  and  applied  while 
wet  with  a  camels'  hair  pencil.  The  gum  with  which  they 
are  mixed  causes  them  to  adhere  so  closely  to  the  paper  that 
they  cannot  be  rubbed  off. 

Distemper. — Painting  in  distemper  is  used  for  works  to  be 
executed  upon  a  larger  scale,  such  as  stage  scenery,  the  walls 
of  apartments,  &ic.  The  colors  are  used  in  the  form  of  pow- 
der, and  are  mixed  with  water  rendered  glutinous  by  size,  or 
other  solutions  of  animal  glue.  The  mixture  requires,  in 
many  cases,  to  be  used  warm,  as  the  solution  becomes  stiff  upon 
cooling.  Skimmed  milk  also  serves  as  a  vehicle  for  painting 
in  distemper,  and  its  tenacity  is  increased  by  adding  small  por- 
tions of  hme,  and  of  linseed  or  poppy  oil.  The  mixture  dries 
speedily,  the  oil  being  converted  into  a  soap  by  the  lime.* 
Distemper  in  hadigeon  is  employed  by  the  French  to  restore 
the  original  color  to  stone  walls  which  have  become  brown  by 

*This  method  is  highly  recommended  by  Tingry  who  gives  the  following 
recipe.  Skimmed  milk  4  pounds  ;  lime  newly  slaked  6  ounces  ;  linseed,  nut 
or  poppy  oil  4  ounces  ;  Spanish  white  (white  clay)  3  pounds. 


432 


ARTS  OF  COMMUNICATING 


time  ;  and  consists  in  washing  them  with  powder  of  the  same 
kind  of  stone,  properly  mixed.  Chipolin  is  a  varnished  dis- 
temper. 

Fresco. — Paintings  in  fresco  are  executed  upon  walls  recent- 
ly plastered,  before  they  have  become  dry.  The  coloring 
substance  mixed  with  water  being  applied  while  the  wall  is 
wet,  sinks  in  and  incorporates  itself  with  the  grain  of  the  mor- 
tar, so  as  to  become  very  durable.  When  a  wall  is  to  be  done 
in  fresco  it  is  covered  with  a  coating  of  stucco  or  fine  mortar, 
which  is  applied  in  successive  portions,  no  more  being  put  on 
at  once  than  can  be  painted  before  it  is  dry.  This  mode  of 
finishing  by  piecemeal,  renders  it  necessary  that  the  artist 
should  have  his  whole  design  either  drawn  upon  paper,  or  thor- 
oughly digested  in  his  mind  before  he  begins.  The  drawings 
which  are  executed  upon  large  paper  to  serve  as  patterns  for 
fresco  paintings,  are  called  cartoons.  They  are  transferred  to 
the  walls  by  puncturing  through  the  outlines  with  a  sharp  point*  * 
Many  of  the  greatest  works  of  the  most  eminent  Italian  mas- 
ters are  executed  in  fresco,  upon  the  walls  and  ceilings  of  the 
different  churches  and  cathedrals. 

Encaustic  Painting. — The  ancients  made  use  of  a  mode 
denominated  encaustic  painting,  the  knowledge  of  which  at 
the  present  day  is  lost.  From  the  writings  of  Pliny  it  appears 
that  the  material  with  which  the  colors  were  incorporated,  was 
wax,  and  that  this  was  applied  by  the  assistance  of  heat.  It 
is  represented  as  having  been  very  brilliant  and  durable,  though 
no  specimens  of  it  remain  at  this  day.  The  principal  paint- 
ings which  have  been  discovered  upon  the  walls  at  Herculaneum 
and  Pompeii,  appear  to  have  been  done  in  fresco. 

Oil  Painting. — Painting  in  oil,  which  on  many  accounts 
has  a  great  superiority  over  other  methods,  was  first  applied  to 
the  execution  of  designs  about  the  year  1410,  by  John  Van 
Eyck,  in  Flanders.  The  oils  used  for  painting  must  be  of  the 
class  denominated  drying  oils.    Of  these,  linseed  oil  is  the 

*  Cartoons  are  also  used  as  patterns  in  tapestry  and  mosaic. 


AND  MODIFYING  COLOR. 


433 


kind  most  commonly  employed,  and  its  tendency  to  dry  is 
increased  by  its  being  boiled.  Its  color  renders  it  sometimes 
injurious  to  light  tints,  so  that  in  delicate  pieces  it  is  better 
to  employ  nut  oil,  or  poppy  oil,  which  are  nearly  trans- 
parent, and  do  not  turn  dark  in  drying.  The  drying  of  paint 
is  owing,  not  so  much  to  evaporation,  as  to  a  chemical  combi- 
nation of  the  oil  with  the  pigment,  especially  when  the  latter 
is  a  metallic  oxide,  or  other  substance,  having  a  direct  affinity 
for  the  oil.  The  oxygen  of  the  atmosphere  appears  also  to 
enter  into  this  combination.  The  drying  will  be  frustrated  if 
a  small  quantity  of  any  fat  oil  be  present.  Hence  in  painting 
old  surfaces,  w^hich  have  been  exposed  to  contract  any  greasi- 
ness,  it  is  necessary  first  carefully  to  cleanse  them,  or  to  wash 
them  with  lime  in  water,  or  with  some  alkaline  solution, 
which  combines  with  the  oil.  The  latter  method  is  practised 
by  house  painters. 

Oil  paintings  of  designs  are  executed  either  on  canvass, 
on  wood,  or  on  copper.  When  the  colors  used  are  chiefly 
of  the  kind  denominated  body  colors,  each  successive  layer 
conceals  those  beneath  it,  so  that  the  work  may  be  height- 
ened, amended,  or  altered,  at  pleasure  during  any  stage  of 
the  process.  Paintings  in  oil  are  very  durable,  and  acquire 
a  mellowness  from  age  which  improves  rather  than  injures  their 
effect,  provided  permanent  colors  have  been  used. 

Painting  in  the  large  way,  with  uniform  colors  mixed  in  oil, 
is  employed  not  so  much  for  ornament,  as  for  the  protection  of 
perishable  substances  from  decay.  Thus  wood  may  be  pre- 
served from  decomposition,  and  metals  from  oxidation,  for  an 
indefinite  time,  by  keeping  them  covered  with  a  thick  coating 
of  paint,  which  is  impervious  to  air  and  moisture. 

V^arnishing. — The  name  of  varnishes  is  given  to  certain 
compounds,  chiefly  solutions  of  resinous  substances,  which 
after  being  spread  over  surfaces,  and  dried,  possess  the  quali- 
ties of  hardness,  brilliancy,  and  transparency.  They  are  em- 
ployed to  give  lustre  and  smoothness  to  painted  surfaces,  an(i 
to  defend  them  from  the  action  of  the  air. 
55 


434 


IRTS   OF  COMMUNICATING 


The  principal  substances  which  form  the  basis  of  varnishes, 
are  copal,  mastic,  anime,  sandarac,  lac,  benzoin,  amber,  and 
asphaltum.  Of  these,  copal  is  a  hard,  shining,  transparent  resin, 
of  a  light  citron  color,  originally  brought  from  Spanish  America^ 
and  erroneously  considered  as  the  product  of  the  Rhus  copal- 
linum.  *  True  copal  is  soluble  in  oil,  but  is  difficult  of  solu- 
tion in  alcohol.  It  is  commonly  made  into  varnish  by  dissolv- 
ing it  in  hot  linseed  oil,  rendered  drying  by  quickhme,  and 
diluting  the  solution  with  oil  of  turpentine.  By  mixture  with 
camphor,  it  becomes  soluble  in  alcoiiol,  or  in  oil  of  turpentine. 
Mastic  is  a  resinous  substance,  in  the  form  of  tears,  of  a  pale 
yellow  color,  brittle  and  semitransparent.  It  comes  from  the 
Levant,  and  is  produced  by  the  Pistacia  lentiscus.  A  greater 
part  of  it  is  soluble  in  alcohol  and  in  oil  of  turpentine.  *dnime 
is  brought  from  Spanish  America,  and  is  said  to  be  obtained 
from  the  Hymencea  courharil.  It  resembles  copal  very  much 
in  its  appearance,  but  is  easily  soluble  in  alcohol,  while  copal 
is  not.  It  is  often  sold  under  the  name  of  copal..  Sandarac 
is  the  resin  of  the  Thuya  articulata  which  grows  in  Barbary. 
It  resembles  mastic,  but  is  rather  more  transparent  and  britde. 
When  chewed,  it  crumbles  to  powder,  whereas  mastic  softens 
in  the  mouth.  It  is  soluble  in  alcohol,  and  oil.  Lac  is  depos- 
ited on  certain  trees  in  the  East  Indies,  by  an  insect  called 
Coccus  lacca.  The  substance  in  its  natural  state  incrusting 
the  twigs,  is  called  stick  lac;  when  broken  off  and  boiled  in 
water,  till  it  loses  its  red  color,  it  is  termed  seed  lac,  and  when 
melted  and  reduced  to  a  thin  crust,  it  is  called  shell  lac.  Stick 
Jac  has  a  deep  red  color,  and  yields  to  water  a  red  substance 
which  is  used  as  a  dye.  Lac  is  soluble  in  alcohol.  Benzoin 
is  the  product  of  the  Styrax  benzoe,  diiree  growing  in  Sumatra. 
It  is  a  solid,  brittle  substance,  in  yellowish  white  tears,  joined 

*  The  Rhus  copallinum  is  a  common  shrub  in  the  United  States,  and  is  not 
known  to  produce  any  substance  resembling  copal.  According  to  Hernandez 
the  copal  of  Spanish  America  is  obtained  from  various  trees.  I  am  informed 
that  the  copal  used  in  this  country  comes  almost  wholly  from  the  East  Indies. 
It  is  probably  the  produce  of  the  Elesocarpus  copalifera. 


AND  MODIFYING  COLOR. 


436 


together  by  a  brown  substance,  and  is  sometimes  wholly  brown. 
It  is  a  balsam,  and  affords  benzoic  acid.  Amber  and  asphalium 
are  mineral  substances,  already  mentioned  in  the  first  chapter. 

Varnishes  are  divided  into  three  kinds,  according  to  the 
menstruum  in  which  the  resinous  substance  is  dissolved.  These 
are  spirit  varnishes,  in  w^hich  the  solvent  is  alcohol ;  essential 
varnishes  in  which  a  volatile  oil,  commonly  oil  of  turpentine,  is 
used  ;  and  oil  varnishes,  which  consist  of  a  resin  dissolved  in  a 
drying  oil.  Some  vegetable  juices  may  be  applied  in  their 
liquid  state.  Thus  the  viscid  juice  of  the  Rhus  vernix  affords 
the  celebrated  black  varnish  used  in  Japan.  The  same  shrub, 
which  grows  in  this  country,  affords  a  whitish  juice,  which, 
upon  boiling,  yields  a  strong,  glossy  black  varnish.  * 

An  elastic  varnish  may  be  made  by  dissolving  caoutchouc 
in  linseed  oil  and  oil  of  turpentine  ;  but  this  preparation  dries 
slowly.  Besides  the  solvents  mentioned  in  the  first  chapter  of 
this  work,  it  is  found  that  the  naptha  of  coal  tar  dissolves 
caoutchouc  readily,  and  on  drying  leaves  its  properties  un- 
altered, f 

Japanning. — Japanning  is  the  art  of  varnishing  in  colors, 
and  is  therefore  a  species  of  painting.  It  is  most  easily  exe- 
cuted upon  wood  and  metal,  or  such  other  substances  as  retain 
a  determinate  form,  and  are  capable  of  sustaining  the  operation 
of  drying  the  varnish.  Paper  and  leather,  when  wrought 
into  forms  in  which  they  remain  stretched,  stiff,  or  inflexible, 
are  common  subjects  for  japanning. 

The  article  to  be  japanned  is  first  brushed  over  with  two  or 
three  coats  of  seed  lac  varnish,  to  form  the  priming.  It  is 
then  covered  with  varnish  previously  mixed  with  a  pigment  of 
the  lint  desired.  This  is  called  the  ground  color ;  and  if  the 
subject  is  to  exhibit  a  design,  the  objects  are  painted  upon 
it,  in  colors  mixed  with  varnish,  and  used  in  the  same  manner  as 
for  oil  painting.    The  whole  is  then  covered  with  additional 

*  See  American  Medical  Botany,  vol.  i.  p.  101.    The  shrub  is  poisonous  ta 
many  persons, 
t  Annals  of  Philosophy,  vol.  xii. 


436 


ARTS  OF  COMMUNICATING 


coats  of  transparent  varnish,  and  all  that  remains  to  he  done, 
is  to  dry  and  polish  it. 

Japanning  requires  to  be  executed  in  warm  apartments,  and 
the  articles  are  warmed  before  the  varnish  is  applied  to  them. 
One  coat  of  varnish,  also,  must  be  dry  before  another  is  laid 
on.    Ovens  are  employed  to  hasten  the  drying  of  the  work. 

The  same  pigments  which  are  employed  in  oil  or  water, 
answer  also  in  varnish.  For  painting  figures,  shell  lac  varnish 
is  considered  best,  and  easiest  to  work ;  it  is  therefore  employ- 
ed in  most  cases  where  its  color  permits.  For  the  lightest 
colors,  mastic  varnish  is  employed,  unless  the  fineness  of  the 
work  admits  the  use  of  copal  dissolved  in  alcohol. 

Polishing. — Pictures,  and  other  subjects,  to  which  only  a 
thin  coat  or  two  of  varnish  is  given,  are  generally  left  to  the 
polish  which  the  varnish  naturally  possesses,  or  are  brightened 
only  by  rubbing  them  with  a  woollen  cloth  when  dry.  But  when- 
ever several  coats  of  varnish  or  japan  are  laid  on,  a  more 
glossy  surface  can  be  produced,  by  means  similar  to  those 
which  are  used  to  polish  metals ;  the  surface  having  first  been 
suffered  to  become  completely  dry  and  hard.  Where  the 
coat  of  varnish  is  very  thick,  the  surface  is  first  rubbed  with 
pumice  stone  and  oil,  till  it  becomes  uniformly  smooth ;  the 
pumice  having  been  previously  reduced  to  a  smooth  flat  face, 
by  rubbing  it  on  freestone.  The  japanned  or  varnished  sur- 
face may  afterwards  be  rubbed  with  pumice  reduced  to  an 
impalpable  powder,  the  workman  using  oil  and  leather  to  lay 
on  the  powder.  The  finishing  may  be  given  by  oil  and  a 
piece  of  woollen  only. 

Where  the  varnish  is  thinner,  and  of  a  more  delicate  nature, 
it  may  be  rubbed  with  tripoli,  or  rotten  stone,  in  fine  powder, 
finishing  with  oil  as  before.  Where  the  ground  is  white,  putty, 
or  Spanish  white,  finely  washed,  may  be  used  instead  of  rotten 
stone,  of  which  the  color  might  have  some  tendency  to  injure 
the  ground. 

Lacquering. — Lacquering  consists  in  the  application  of 
transparent  varnishes  to  metals,  to  prevent  their  tarnishing,  or 


AND  MODIFYING  COLOR. 


437 


to  give  them  a  more  agreeable  color.  When  the  color  of  the 
metal  to  be  lacquered  is  to  be  changed,  the  varnish  is  tinged 
with  some  coloring  matter  ;  but  where  preservation  from  rust, 
or  tarnish,  is  the  sole  object,  any  of  the  transparent  varnishes 
will  answer,  the  best  and  hardest  being  used  where  the  greatest 
durability  is  required.  Shell  lac  is  the  most  common  basis  of 
the  varnishes  used  in  lacquering.  An  imitation  of  gilding  is 
effected  by  covering  the  surface  of  tin  or  lead  with  a  clear 
varnish  tinged  with  annotto,  turmeric,  or  gamboge.  The 
Chinese  gilt  paper  appears  to  be  made  in  this  manner. 

Gilding. — The  process  of  gilding  on  metals,  described  in  a 
former  chapter,  depends  on  a  chemical  union,  or  alloy,  between 
the  gold  and  the  metal  to  which  it  is  applied.  But  gilding  as 
it  is  commonly  performed  upon  wood,  leather,  he,  is  a  me- 
chanical process,  and  consists  in  cementing  gold  leaf  upon 
surfaces,  for  which  it  has  no  affinity.  In  common  oil  gilding, 
the  surface  to  be  gilt  is  covered  with  an  adhesive  coating  of 
paint  or  gold  size,  composed  of  yellow  ochre  ground  in  oil. 
When  this  is  partially  dried,  so  as  to  feel  adhesive,  the  gold 
leaf  is  laid  upon  it  and  pressed  down  with  cotton  wool.  When 
the  whole  surface  is  covered,  it  is  left  to  dry,  and  the  superflu- 
ous gold  leaf  brushed  off.  In  burnish  gilding,  the  surface  to 
be  gilt  is  first  covered  with  a  mixture  of  whiting  and  size, 
prepared  by  boiling  shreds  of  parchment  or  skins,  in  water. 
This  is  rubbed  smooth  and  covered  with  a  gilding  size  contain- 
ing a  little  ochre  or  Armenian  bole.  This  is  suffered  to  dry 
and  is  rubbed  smooth  with  a  linen  rag.  The  gilding  is  then 
performed  by  moistening  successively  the  parts  of  the  sized 
surface  with  water,  and  applying  the  gold  leaf  before  it  becomes 
dry.  When  the  work  has  become  firm,  it  is  burnished  by 
rubbing  it  with  a  hard  polished  substance,  such  as  agate,  dog's 
tooth,  or  steel. 

Gilding  on  leather  and  on  paper  may  be  performed  by  ap- 
plying gold  leaf  with  gum  arable  or  size.  The  edges  of  paper 
and  of  books  are  gilded  with  a  size  composed  of  whites  of 
eggs,  beaten  with  three  or  four  times  their  quantity  of  water, 


438 


ARTS  OF  COMMUNICATING 


and  mixed  with  a  little  Armenian  bole.  Bookbinders  gild  the 
leather  of  books  by  coating  it  two  or  three  times  with  whites  of 
eggs,  and  suffering  it  to  dry.  A  minute  quantity  of  tallow  is 
then  rubbed  on  and  the  gold  leaf  laid  loosely  upon  the  surface. 
The  stamps  and  letters  are  cut  in  brass ;  or  printing  types  are 
used.  These  are  moderately  heated,  as  much  as  the  leather 
will  bear,  and  are  then  pressed  upon  the  gold  leaf,  by  which  a 
portion  of  gold  corresponding  to  the  letters  is  made  to  adhere  ; 
after  which  the  superfluous  gold  leaf  is  brushed  off. 

Shell  gold  is  prepared  by  grinding  up  gold  leaf  with  honey 
until  it  is  completely  subdivided  ;  the  honey  is  then  washed 
away  with  water  and  the  gold  powder  mixed  with  gum  water 
or  some  other  adhesive  fluid.  It  is  usually  kept  for  use  on 
shells,  and  is  applied  with  a  pencil  or  brush  in  the  manner  of 
common  painting. 

OF   CHANGING  INTRINSIC  COLOR. 

The  processes  considered  in  the  previous  part  of  this  chap- 
ter, are  used  to  produce  an  external  modification  of  color, 
and  consist  in  mechanically  covering  the  surfaces  upon  which 
they  are  applied.  The  remaining  division  includes  those  arts, 
which  depend  more  exclusively  upon  chemical  processes,  and 
which,  by  operating  on  the  internal  texture  of  bodies,  produce 
a  total  and  intrinsic  change  of  color.  Of  this  kind  are  the 
arts  of  bleaching,  dyeing,  and  calico  printing.  The  operations, 
however,  which  belong  to  these  arts,  are  too  extensive  to  be 
considered  in  all  their  details  in  this  place. 

Bleaching. — Bleaching  is  the  process  by  which  fibrous  tex- 
tures, such  as  linen,  cotton,  silk,  &;c.  are  deprived  of  their  col- 
or, and  rendered  white.  The  coloring  matter,  which  is  inhe- 
ent  in  vegetable  fibres,  appears  to  be  of  a  resinous  character,  and 
the  effect  of  the  operation  of  bleaching  is  to  dissolve,  or  dis- 
charge it.  In  manufactories  of  linen  and  cotton  goods,  the 
yarn  or  cloth  passes  through  a  number  of  successive  processes, 
the  principal  of  which  are  the  steeping,  in  which  the  goods  are 


AND  MODIFYING  COLOR. 


439 


fermented  in  an  acescent  liquid  at  a  temperature  of  about  100 
degrees,  Fahrenheit — the  lucking  and  boiling,  in  which  a  hot 
alkaline  ley  is  made  to  percolate  through  them  for  some  time — 
the  souring,  performed  with  diluted  sulphuric  acid — the 
bleaching  with  chlorine,  in  which  the  stuff  is  exposed  to  the 
action  of  some  compound  of  that  substance,  usually  chloride 
of  lime,  called  bleaching  salt.  Various  mechanical  operations, 
washings,  and  repetitions  of  the  processes,  are  commonly  prac- 
tised to  complete  the  discharge  of  the  color.  Formerly  the 
process  of  bleaching  was  very  tedious,  and  was  effected  by 
alkaline  leys  and  by  exposure  to  the  sun  and  air,  with  frequent 
irrigations,  for  many  weeks.  The  discovery  of  the  bleaching 
power  of  chlorine,  has  greatly  abridged  and  simplified  the 
process. 

Chemists  explain  the  effect  of  chlorine  in  bleaching,  *  by 
supposing  that  it  unites  with  the  hydrogen  of  the  coloring 
matter,  and  forms  muriatic  acid,  which  again  acts  upon  the 
color  in  its  altered  state.  The  acid  may  be  detected  in  the 
altered  coloring  matter.  In  bleaching  which  is  performed  by 
exposure  to  the  air  and  moisture,  it  is  supposed  that  oxygen 
combines  with  the  coloring  matter,  and  renders  a  portion  of  it 
more  easy  of  solution,  during  the  other  parts  of  the  process* 

The  fibres  of  wool  and  silk  are  not  bleached  by  chlo- 
rine, but  after  being  deprived  of  the  saponaceous,  or  gummy 
matter,  which  adheres  to  them,  are  exposed  to  the  fumes  of 
bun  'ng  sul])h'!r  to  disoh- rge  tl  eir  color. 

Dyeing. — The  art  of  dyeing  consists  in  impregnating  cloths 
and  other  flexible  fabrics,  with  coloring  substances,  in  such  a 
manner,  that  the  acquired  color  may  remain  permanent  under 
the  common  exposures,  to  which  the  stuffs  may  be  liable.  It 
is  effected  by  producins;  a  chemical  union  between  the  material 
to  be  dyed  and  the  coloring  matter.  It  is  found  that  different 
materials  not  only  possess  different  attractions  for  dye  stuffs, 

*  Gay  Lussac,  Cours  de  Chimie,  Lec.  30,  p.  21. — Ure's  Notes  to  Berthol- 
let,  ii.  344. 


440 


ARTS  OF  COMMUNICATING 


but  that  they  absorb  the  coloring  matter  in  different  proportions. 
Wool  appears  in  this  respect  to  have  the  greatest  attraction  for 
coloring  substances ;  silk  coines  next  to  it,  then  cotton,  and 
lastly  hemp  and  flax. 

Mordants. — The  coloring  substances  used  in  dyeing,  have 
been  divided  by  Dr  Bancroft  into  substantive  and  adjective 
colors.  Substantive  colors  are  those  which  communicate  their 
tint  immediately  to  the  material  to  be  dyed,  without  the  aid  of 
any  third  substance.  Adjective  colors  require  the  intervention 
of  a  third  substance,  which  possesses  a  joint  attraction  for  the 
coloring  matter  and  the  stuff  to  be  dyed.  The  substance  ca- 
pable of  thus  fixing  the  color,  is  called  a  mordant,  and  by  Mr 
Henry,  a  basis. 

The  agents  which  are  capable  of  acting  in  some  way  as 
mordants,  are  very  numerous,  including  many  oxides  and  salts. 
But  those  which  are  principally  employed  in  practice,  are  the 
acetate  of  alumina,  the  sulphate  or  acetate  of  iron,  and  the 
muriate  of  tin.  The  substance  to  be  dyed  is  first  impregnated 
with  the  mordant,  and  then  passed  through  a  solution  of  the 
coloring  matter.  The  mordant  fixes  the  color,  and,  in  many 
cases,  alters  or  improves  and  heightens  its  tint. 

Dyes. — The  coloring  substances  capable  of  being  used  as 
dyes,  are  very  numerous,  but  a  few  of  the  most  important  have 
in  practice  taken  precedence  of  the  rest.  Indigo,  madder, 
quercitron,  and  some  of  the  woods  are  consumed  in  vast  quan- 
tities by  dyers,  and  are  capable  of  producing  an  indefinite  va- 
riety of  tints,  under  the  action  of  different  mordants.  They 
are  somewhat  differently  treated  according  as  the  substance  to 
be  dyed  is  of  wool,  silk,  or  cotton. 

Blue  Dyes. — Indigo  is  the  chief  substance  employed  for  giving  the 
blue  dye.  The  best  indigo  is  obtained  from  a  plant  cultivated  in  warm 
climates,  the  indigo/era  tindoria.  The  plant  is  cut  a  short  time  before 
its  flowering,  and  is  put  into  large  vats  covered  with  water,  when  fer- 
mentation spontaneously  ensues,  during  which  the  indigo  subsides  in 
the  form  of  a  pulverulent,  pulpy  matter.  Its  color  is  at  first  green, 
but  by  exposure  to  the  air,  it  absorbs  oxygen  and  becomes  blue. 


AND  MODIFYING  COLOR. 


441 


Indigo  is  a  light  brittle  substance,  of  a  deep  blue  color,  and  without 
either  taste  or  odor.  At  550  degrees  Fahrenheit  it  sublimes,  forming 
a  violet  vapor  with  a  tint  of  red,  and  condensing  into  long  flat  acicular 
crystals,  which  appear  red  by  reflected,  and  blue  by  transmitted  light. 
The  process  of  subliming  indigo  is  one  of  considerable  delicacy,  owing 
to  the  circumstance  that  the  temperature  at  which  it  sublimes,  is  very 
near  that  at  which  it  is  decomposed.  Indigo  in  its  dry  state,  may  be 
preserved  without  change ;  but  when  kept  under  water  it  is  gradually 
decomposed.  It  is  quite  insoluble  in  water  and  alcohol,  and  is  attack- 
ed by  the  alkalies  in  a  partial  manner.  Its  only  proper  solvent  is  con- 
centrated sulphuric  acid.  When  indigo  is  put  into  this  acid,  a  yellow 
solution  is  at  first  formed,  which,  after  a  few  hours,  acquires  a  deep 
blue  color.  If  the  indigo  is  pure,  sulphurous  acid  is  not  generated, 
nor  is  the  acid  decomposed  ;  but  the  indigo  undergoes  a  change,  for  it 
is  rendered  soluble  in  water.  To  the  indigo  thus  modified,  Mr  Crum 
has  applied  the  name  cenilin,  and  he  regards  it  as  a  compound  of  one 
atom  of  indigo  and  four  atoms  of  water.  This  solution  properly  diluted 
with  water,  is  employed  by  dyers  for  forming  what  is  called  the  Saxon 
blue.  Mr  Crum  has  also  described  another  compound  of  indigo  and 
water,  under  the  name  of  Ph(Bnecin,  because  it  acquires  a  purple  color 
on  the  addition  of  a  salt.  It  appears  to  consist  of  one  atom  of  indigo 
and  two  atoms  of  water. 

When  indigo,  suspended  in  water,  is  brought  into  contact  with  cer- 
tain deoxidizing  agents,  it  is  deprived  of  oxygen,  becomes  green,  and 
is  rendered  soluble  in  water,  and  still  more  in  the  alkalies.  This  effect 
is  produced  for  example,  by  sulphuretted  hydrogen,  by  the  hydrosul- 
phuret  of  ammonia,  by  the  protoxide  of  iron,  precipitated  by  lime  or 
potass,  or  by  a  solution  of  the  sulphuret  of  arsenic  in  potass.  On 
dipping  cloth  into  a  solution  of  deoxidized  indigo,  it  receives  a  green 
tint,  which  becomes  blue  by  exposure  to  the  air.  This  is  the  usual 
method  of  dyeing  blue  by  means  of  indigo,  a  color  which  adheres  per- 
manently to  cloth  without  the  intervention  of  a  basis. 

fVoad  is  prepared  from  the  leaves  of  the  Isatis  tindoria,  a  plant 
cultivated  in  Europe.  Gay  Lussac,  and  others,  consider  it  chemically 
as  a  species  of  indigo.  It  is  prepared  by  grinding,  and  several  pro- 
cesses of  fermentation.  Cloth  dyed  in  woad  liquor  is  at  first  green, 
but  turns  blue  on  exposure  to  the  air,  in  the  same  manner  which  takes 
place  with  indigo. 

Red  Dyes. — The  chief  substances  which  are  employed  for  giving  a 
red  dye,  are  madder,  cochineal,  archil,  Brazil  wood,  logwood,  and  saf- 
flower,  all  of  which  are  adjective  colors. 

Madder,  which  is  one  of  the  most  valuable  drugs  in  the  art  of  dye- 
ing, is  the  root  of  the  Rubia  tindorum,  a  plant  extensively  cultivated 
56 


442 


ARTS   OF  COMMUNICATING 


in  Europe,  and  particularly  in  Holland.  It  is  properly  classed  with 
red  dyes,  but  by  the  use  of  different  mordants,  it  is  made  to  produce 
every  shade  of  red,  purple,  and  even  black.  In  calico  printing  a  piece 
may  be  stamped  with  several  mordants,  which  are  bases  of  different 
colors ;  and  upon  immersing  it  in  a  madder  bath,  as  many  colors  will 
appear,  as  there  are  mordants  used.  The  quality  of  madder  is  said  to 
be  improved  by  age,  provided  it  is  kept  packed  in  casks  which  exclude 
the  air.  Its  quality  is  also  affected  by  the  mode  of  cultivating,  and 
curing  it,  and  the  judgment  which  is  used  in  separating  the  samples. 

Cochineal  is  obtained  from  an  insect  already  mentioned,  which  feeds 
upon  the  leaves  of  several  species  of  the  cactus,  and  which  is  suppos- 
ed to  derive  this  coloring  matter  from  its  food.  It  is  very  soluble  in 
water,  and  is  fixed  on  cloth  by  means  of  alumina  or  the  oxide  of  tin. 
Its  natural  color  is  crimson,  but  when  the  bitartrate  of  potass  is  added 
to  the  solution,  it  yields  a  rich  scarlet  dye.  Cochineal  according  to 
Pelletier  and  Caventou,  is  composed  of,  1.  Carminium,  which  is  the 
name  given  to  the  coloring  matter.  2.  A  peculiar  animal  matter.  3.  A 
fatty  substance.  4.  Salts  of  lime  and  potass. 

Archil. — The  dye  called  archil,  is  obtained  from  a  kind  of  lichen, 
(lichen  roccella)  which  grows  chiefly  in  the  Canary  Islands,  and  is  em- 
ployed by  the  Dutch  in  forming  the  blue  pigment  called  litmus  or 
turnsol.  The  coloring  ingredient  of  litmus  is  a  compound  of  the  red 
coloring  matter  of  the  lichen  and  an  alkali ;  and  hence,  on  the  addition 
of  an  acid,  the  coloring  matter  is  set  free,  and  the  red  tint  of  the  plant 
is  restored.  Litmus  is  not  only  used  as  a  dye,  but  is  employed  by 
chemists  for  detecting  the  presence  of  a  free  acid. 

Logwood  is  a  dense,  heavy  wood,  derived  from  the  Hcematosylum 
Campechianum,  which  grows  in  the  tropical  parts  of  America.  A 
decoction  made  from  this  wood,  is  of  a  fine  red,  inclining  a  little  to 
violet  or  purple.  This,  if  left  to  itself,  becomes  in  time  yellowish, 
and  at  length  black.  The  violet  color  of  logwood  is  fixed  by  alum, 
and  a  blue  is  obtained  from  it  by  verdigris.  But  the  great  consump- 
tion of  logwood  is  for  blacks,  to  which  it  gives  a  peculiar  depth,  and 
velvety  lustre.  The  coloring  principle  of  logwood  has  been  procured 
in  a  separate  state  by  M.  Chevreul,  who  has  applied  to  it  the  name  of 
hematin.  It  is  obtained  in  crystals  by  digesting  the  aqueous  extract  of 
logwood  in  alcohol,  and  allowing  the  alcoholic  solution  to  evaporate 
spontaneously. 

Brazil  wood  is  the  heart,  or  central  part  of  the  Ccesalpinia  echinata, 
a  large  tree  of  Brazil.  It  produces  very  lively  and  beautiful  red  tints 
with  solutions  of  alumina  and  tin,  but  they  are  deficient  in  permanency. 
Sappan  wood  brought  from  the  East  Indies,  and  JVicaragua  wood,  or 
Peachwood,  from  Central  America,  are  also  said  to  be  species  of  Cse- 


AND  MODIFYING  COLOR. 


443 


salpinia,  and  resemble  Brazil  wood  in  their  properties,  but  yield  a 
smaller  amount  of  coloring  matter.  Braziletto  and  Camwood,  are 
among  the  poorest  of  the  red  dyes. 

Safflower  is  the  dried  flowers  of  the  Carthamus  tindorius,  a-nd  affords 
a  bright  but  fugitive  red.    See  Rouge. 

Yellow  Dyes. — The  chief  yellow  dyes  are  the  quercitron  bark,  tur- 
meric, hickory,  weld,  fustic,  and  satfron.    They  are  all  adjective  colors. 

Quercitron  bark,  which  is  one  of  the  most  important  of  the  yellow 
dyes,  is  an  extract  made  from  the  bark  of  the  Quercus  tindoria,  or 
common  black  oak  of  the  United  States,  and  was  introduced  into  no- 
tice by  Dr  Bancroft.  With  a  basis  of  alumina,  the  decoction  of  this 
bark  gives  a  bright  yellow  dye.  With  the  oxide  of  tin  it  communicates 
a  variety  of  tints,  which  may  be  made  to  vary  from  a  pale  lemon  color 
to  deep  orange.    With  the  oxide  of  iron  it  gives  a  drab  color. 

Hickory. — Several  species  of  American  walnut  or  hickory,  particu- 
larly the  Juglans,  or  Carya  alba,  yield  a  yellow  dye  from  their  bark, 
leaves,  and  rinds,  resembling  quercitron,  but  less  abundant  in  quantity. 

fVeld  is  derived  from  a  European  plant.  Reseda  luteola.  When  fixed 
with  a  basis  of  alum,  it  gives  a  lively  and  permanent  yellow. 

Fustic  is  the  wood  of  the  Morus  tindoria,  a  tree  of  the  West  In- 
dies. It  affords,  with  an  aluminous  basis,  a  less  brilliant,  but  more 
durable  yellow,  than  the  preceding  articles.  It  is  also  employed  to 
produce  certain  greens  and  drab  colors. 

Annotto,  otherwise  called  Rocou,  is  a  soft  substance  prepared  from 
the  seeds  of  the  Bixa  orellana,  a  shrub  of  tropical  America.  The 
coloring  matter  is  combined  with  a  resin  which  renders  it  difficult  of 
solution  in  water.  An  alkali  facilitates  the  solution  and  improves  the 
color. 

Turmeric  is  the  root  of  the  Curcuma  longa,  a  native  of  the  East 
Indies.  Paper,  stained  with  a  decoction  of  this  substance,  constitutes 
the  turmeric  or  curcuma  paper  employed  by  chemists  as  a  test  of  free 
alkali ;  by  the  action  of  which  it  receives  a  brown  stain. 

Saffron. — The  coloring  ingredient  of  saffron  (Crocus  sativus)  is  solu- 
ble in  water  and  alcohol,  has  a  bright  yellow  color,  is  rendered  blue 
and  then  lilac  by  sulphuric  acid,  and  receives  a  green  tint  on  the 
addition  of  nitric  acid.  From  the  great  diversity  of  colors  which  it  is 
capable  of  assuming  under  different  circumstances,  M.  M.  Bouillon, 
Lagrange,  and  Vogel,  have  proposed  for  it  the  name  of  Polychroite. 

French  Bennies. — The  unripe  berries  of  the  Rfiamnus  ivfedorius, 
afford  a  lively  but  fugitive  yellow. 

Black  Dyes. — The  black  dye  is  made  of  the  same  ingredients  as 
writing  ink,  and  therefore  contains  usually  a  compound  of  the  oxide 


444 


ARTS  OF  COMMUNICATING 


of  iron  with  gallic  acid  and  tannin.  From  the  addition  of  logwood 
and  acetate  of  copper,  the  black  receives  a  shade  of  blue. 

Galls. — The  common  nutgall  is  an  excrescence  produced  upon  an 
Asiatic  species  of  oak,  {Quercus  infecloiia)  by  the  puncture  of  an  in- 
sect, a  species  of  cynips.  It  contains  tannin,  gallic  acid,  and  accord- 
ing to  Dr  Bancroft,  a  coloring  matter  distinct  from  these.  Galls  pro- 
duce a  black  color  with  salts  of  iron,  well  known  as  the  basis  of  writ- 
ing ink. 

Maple. — The  common  red  maple  of  this  country  (Acerruhrum)  \w\ien 
applied  with  the  sulphate  or  acetate  of  iron,  produces,  according  to 
Dr  Bancroft,  a  more  intense  and  perfect  black  than  any  of  the  common 
vegetable  dyes.  With  the  aluminous  basis,  it  produces  a  lasting  cin- 
namon color,  both  on  wool  and  cotton.  Both  the  bark  and  leaves  may 
be  used. 

Butternut. — The  bark  of  the  butternut  (Juglans  cathartica)  affords 
a  durable  brown  upon  cotton  with  an  aluminous  basis,  and  upon  wool 
without  any  mordant. 

By  the  dexterous  combination  of  the  four  leading  colors, 
blue,  red,  yellow,  and  black,  all  other  shades  of  color  may  be 
procured.  Thus  green  is  communicated  by  forming  a  blue 
ground  with  indigo,  and  then  adding  a  yellow  by  means  of 
quercitron  bark. 

One  of  the  latest  improvements  in  the  art  of  dyeing,  con- 
sists in  the  employment  of  colors  derived  from  the  mineral 
kingdom.  Prussian  blue,  orpiment,  chromate  of  lead,  and 
other  mineral  compounds,  have  by  appropriate  processes  been 
made  to  communicate  their  colors  to  different  stuffs.  An  ab- 
stract of  the  processes  is  given  in  Ure's  notes  to  Berthollet  on 
dyeing. 

Calico  Printing. — Calico  printing  is  a  combination  of  the 
arts  of  engraving  and  dyeing,  and  is  used  to  produce  upon 
woven  fabrics,  chiefly  of  cotton,  a  variety  of  ornamental  com- 
binations, both  of  figure  and  color.  In  this  process  the  whole 
fabric  is  immersed  in  the  dyeing  liquid,  but  it  is  previously 
prepared  in  such  a  manner,  that  the  dye  adheres  only  to  the 
parts  intended  for  the  figure,  while  it  leaves  the  remaining 
parts  unaltered.  In  calico  printing,  adjective  colors  are  most 
frequently  employed.    The  cloth  is  prepared  by  bleaching  and 


AND  MODIFYING  COLOR. 


445 


other  processes,  which  dispose  it  to  receive  the  color.  It  is 
then  printed  with  the  mordant,  in  a  manner  similar  to  that  of 
copperplate  printing,  except  that  the  figure  is  engraved  upon  a 
cylinder,  instead  of  a  plate.  The  cylinder,  in  one  part  of  its 
revolution,  becomes  charged  with  the  mordant  mixed  to  a 
proper  consistence  with  starch.  The  superfluous  part  of  the 
mordant  is  then  scraped  off  by  a  straight  steel  edge,  in  contact 
with  which  the  cylinder  revolves,  leaving  only  that  part  which 
remains  in  the  lines  of  the  figure.  The  cloth  then  passes  in 
forcible  contact  with  the  other  side  of  the  cylinder,  and  receives 
from  it  a  complete  impression  of  the  figure  in  the  pale  color  of 
the  mordant.  The  cloth  is  then  passed  through  the  coloring 
bath,  in  which  the  parts  previously  printed  become  dyed  with 
the  intended  color.  When  it  is  afterwards  exposed,  and  wash- 
ed, the  color  disappears  from  those  parts  which  are  not  im- 
pregnated with  the  mordant,  but  remains  permanently  fixed  to 
the  rest.  When  additional  colors  are  required,  they  are  print- 
over  the  rest  with  different  mordants,  suited  to  the  color  in- 
tended to  be  produced.  This  secondary  printing  is  in  most 
instances  performed  with  blocks,  engraved  in  the  manner  of 
wood  cuts,  and  applied  by  hand  to  the  successive  parts  of  the 
piece. 

In  some  articles,  white  spots  upon  a  dark  ground  are  pro- 
duced by  covering  the  parts  with  wax,  tallow,  pipe  clay,  or 
other  materials,  which  prevent  the  contact  of  the  color.  Some- 
times the  color  is  discharged  in  places  by  the  application  of 
chlorine.  A  preparation  of  one  of  the  salts  of  copper,  applied 
in  spots,  or  figures,  has  the  effect  to  oxygenate  indigo,  so  as  to 
render  it  insoluble,  and  consequently  incapable  of  dyeing  these 
spots,  when  the  stulT  is  immersed.  To  these  and  similar  pro- 
cesses, the  name  of  resist  work  has  been  given. 

Fast  Colors. — The  following  are  the  dye  stuffs  used  by  the  calico 
printers  for  producing  fast  colors.  *  The  mordants  are  thickened  with 
gum,  or  calcined  starch,  and  applied  with  the  block,  cylinder,  plates, 
or  otherwise. 

*  Ure's  Dictionary. 


446 


ARTS  OF  COMMUNICATING 


1.  Black.  The  cloth  is  impregnated  with  acetate  of  iron  (iron 
liquor)  and  dyed  in  a  bath  of  madder  and  logwood. 

2.  Purple,  The  preceding  mordant  of  iron,  diluted  ;  with  the  same 
dyeing  bath. 

3.  Crimson.  The  mordant  for  purple,  united  with  a  portion  of  ace- 
tate of  alumina,  or  red  mordant,  and  the  above  bath. 

4.  Red.  Acetate  of  alumina  is  the  mordant,  and  madder  is  the  dye 
stuff. 

5.  Pale  red  of  different  shades.  The  preceding  mordant  diluted 
with  water,  and  a  weak  madder  bath. 

6.  Brown  or  Pompadour.  A  mixed  mordant,  containing  a  somewhat 
larger  proportion  of  the  red  than  of  the  black :  and  the  dye  of  madder. 

7.  Orange.  The  red  mordant ;  and  a  bath  first  of  madder,  and  then 
of  quercitron. 

8.  Yellow.  A  strong  red  mordant ;  and  the  quercitron  bath,  whose 
temperature  should  be  considerably  under  the  boiling  point  of  water. 

9.  Blue.  Indigo,  rendered  soluble  and  greenish  yellow  colored,  by 
potash  and  orpiment.  It  recovers  its  blue  color,  by  exposure  to  air, 
and  thereby  also  fixes  firmly  on  the  cloth.  An  indigo  vat  is  also  made, 
with  that  blue  substance,  diffused  in  water  with  quicklime  and  copperas. 
These  substances  are  supposed  to  deoxidize  indigo,  and  at  the  same 
time  to  render  it  soluble. 

Golden-dye.  The  cloth  is  immersed  alternately  in  a  solution  of 
copperas  and  lime  water.  The  protoxide  of  iron  precipitated  on  the 
fibre,  soon  passes  by  absorption  of  atmospherical  oxygen,  into  the 
golden-colored  deutoxide. 

Buff.    The  preceding  substances,  in  a  more  dilute  state. 

Blue  vat,  in  which  white  spots  are  left  on  a  blue  ground  of  cloth, 
is  made,  by  applying  to  these  points  a  paste  composed  of  a  solution  of 
sulphate  of  copper  and  pipe  clay  ;  and  after  they  are  dried,  immersing 
it  stretched  on  frames  for  a  definite  number  of  minutes,  in  the  yellow- 
ish-green vat,  of  one  part  of  indigo,  two  of  copperas,  and  two  of  lime, 
with  water. 

Green.  Cloth  dyed  blue,  and  well  washed,  is  imbued  with  the  alum- 
inous acetate,  dried,  and  subjected  to  the  quercitron  bath. 

In  the  above  cases,  the  cloth,  after  receiving  the  mordant  paste,  is 
dried,  and  after  some  preparation,  put  into  the  dyeing  vat  of  copper. 

Fugitive  Colors. — All  these  colors  are  given,  by  making  decoc- 
tions of  the  different  coloring  woods  ;  and  receive  the  slight  degree 
of  fixity  they  possess,  as  well  as  great  brilliancy,  in  consequence  of 
their  combination  or  admixture  with  the  nitro-muriate  of  tin. 

1.  Red  is  frequently  made  from  Brazil  and  Peachwood. 

2.  Black.    A  strong  extract  of  galls,  and  deuto-nitrate  of  iron. 


AND  MODIFYING  COLOR. 


447 


3.  Purple,    Extract  of  logwood  and  the  deuto-nitrate. 

4.  Yellow.  Extract  of  quercitron  bark,  or  French  berries,  and  the 
tin  solution. 

5.  Blue.    Prussian  blue  and  solution  of  tin. 

Fugitive  colors  are  thickened  with  gum  tragacanth,  which  leaves 
the  cloth  in  a  softer  state  than  gum  Senegal ;  the  goods  being  some- 
times sent  to  market  without  being  washed. 


Tingry's  Painter  and  Varnisher's  Guide,  8vo.  translated  1816 ; — 
Elmes'  Dictionary  of  Fine  Arts,  8vo.  1826; — James's  Panorama  of 
'  Science  and  Art,  2  vols,  8vo.  1816 ; — Bancroft  on  Permanent  Colors, 
2  vols,  8vo.  1814 ; — Berthollet,  Elements  of  the  Art  of  Dyeing, 
translated  by  Ure,  2  vols,  8vo.  1824  ; — Gay  Lussac,  Cours  de  Chimie, 
2  vols,  8vo.  1828  ; — Brande's  Chemistry,  1820  ; — Turner's  Chemis- 
try, 1828; — Parkes's  Chemical  Essays,  1823; — Ure's  Dictionary; — 
Vi TALIS,  Cours  eUmentaire  deteinture,  1823. 


CHAPTER  XIX. 


ARTS  OF  VITRIFICATION. 

A  great  number  of  earths,  and  other  mineral  bodies,  after 
"being  fused,  do  not  resume  their  original  character  upon  cool- 
ing, but  pass  into  a  dense,  hard,  shining,  and  brittle  state,  hav- 
ing the  character  of  glass ;  and  are  thus  said  to  be  vitrified. 
Most  of  these  substances  do  not  immediately  become  hard, 
upon  the  reduction  of  their  temperature,  but  go  through  an  in- 
termediate, or  ductile  state,  in  which  a  combination  of  soft- 
ness with  tenacity,  enables  them  to  be  wrought  into  articles  of 
use  and  ornament.  Of  these,  common  glass  is  the  most  im- 
portant, while  enamels,  artificial  gems,  &ic.  belong  to  the  same 
species  of  manufacture. 

Glass. — Glass  is  a  compound  substance  artificially  produced 
by  the  combination  of  siliceous  earth  with  alkalies,  and  in  some 
cases  with  other  metallic  oxides.  These  substances  being 
melted  together  at  a  high  temperature,  unite,  lose  their  opacity, 
and  are  fused  into  a  homogeneous  mass,  which  on  cooling  has  ^ 
the  properties  of  hardness,  transparency,  and  brittleness. 

Materials.  * — The  most  important  ingredient,  and  in  fact 
the  basis  of  transparent  glass,  is  silica,  or  oxide  of  silicium. 
This  earth  nearly  in  a  state  of  purity,  is  found  in  the  sand 
of  certain  situations,  and  also  in  common  flint,  and  quartz  peb- 
bles.   Sand  has  the  advantage  of  being  already  in  a  state  of 

*  The  term  metals,  which  appears  to  be  a  corruption  of  materials,  is  in 
common  use  among  glass  manufacturers  to  express  the  ingredients  or  sub- 
stances, upon  which  their  operations  are  performed.  The  same  term  is  em- 
ployed in  a  similar  sense  by  other  manufacturers  and  artists,  and  by  some 
writers  on  road  making.  The  term  metal,  in  the  singular,  is  applied  to  glass 
in  a  state  of  fusion. 


ARTS  OP  VITRIFICATION. 


449 


minute  division,  not  requiring  to  be  pulverized.  Pure  siliceous 
sand  proper  for  the  glass  furnace,  is  found  in  many  localities. 
A  great  portion  of  that  used  in  the  United  States,  is  taken 
from  the  banks  of  the  Delaware.  When  flints  or  quartz  are 
employed,  they  must  be  first  reduced  to  powder,  which  is  done 
by  heating  them  red  hot  and  plunging  them  in  cold  water. 
This  causes  them  to  whiten  and  fall  to  pieces  after  which  they 
are  ground  and  sifted,  before  they  are  ready  for  the  furnace. 

An  alkaline  substance,  either  potash  or  soda,  is  the  second 
ingredient  in  glass.  For  the  finer  kinds  of  glass,  pure  pearl 
ash  is  used,  or  soda  procured  by  decomposing  sea  salt ;  but  for 
the  inferior  sorts,  impure  alkalies  and  even  wood  ashes  are  made 
to  answer  the  purpose.  Lime  is  often  employed  in  small  quan- 
tities, also  borax,  a  salt  which  facilitates  the  fusion  of  the  silica. 

Instead  of  the  common  alkalies,  the  sulphate  of  soda  naay 
be  employed  in  glass  making.  But  in  this  case  it  is  necessary 
to  liberate  the  alkali  by  decomposing  the  sulphuric  acid  of  the 
salt.  This  may  be  done  by  charcoal,  or  in  flint  glass  by  me- 
tallic lead.    Lime  is  also  used  with  this  salt. 

Of  the  metallic  oxides  which  are  added  in  different  cases, 
the  deutoxide  of  lead  (red  lead)  is  the  most  common.  This 
substance  renders  flint  glass  more  fusible,  heavy,  and  tough, 
and  more  easy  to  be  ground  and  cut.  At  the  same  time  it 
imparts  to  it  a  greater  brilliancy,  and  refractive  power.  Black 
oxide  of  manganese  in  small  quantities,  has  the  effect  of 
cleansing  the  glass,  or  of  rendering  it  more  colorless  and 
transparent.  This  effect  it  seems  to  produce  by  imparting 
oxygen  to  the  carbonaceous  impurities,  thus  forming  with  them 
carbonic  acid,  which  subsequently  escapes.  Common  nitre 
produces  a  similar  effect.  If  too  much  manganese  be  added, 
it  communicates  a  purple  tinge  to  the  glass,  which,  however, 
may  be  destroyed  by  a  little  charcoal,  or  wood.  Arsenious 
acid  (white  arsenic)  in  small  quantities,  promotes  the  clearness 
of  glass,  but  if  too  much  be  used,  it  communicates  a  milky 
whiteness.    Its  use  in  drinking  vessels,  is  not  free  from  danger. 


57 


460 


ARTS  OF  VITRIFICATION. 


when  the  glass  contains  so  much  alkali,  as  to  render  any  part 
of  it  soluble  in  acids. 

Crown  Glass. — Glass  is  of  various  kinds,  which  are  named 
not  only  from  the  character  of  their  ingredients,  but  from  the 
mode  in  which  they  are  wrought.  The  name  of  crown  glass 
is  given  to  the  best  kind  of  window  glass,  that  which  is  hardest 
and  most  free  from  color.  It  is  made  almost  entirely  of  sand 
and  alkali,  and  a  little  lime,  without  lead  or  any  other  metalhc 
oxide,  except  a  minute  quantity  of  manganese,  and  sometimes 
of  cobalt,  which  are  added  to  counteract  the  effect  of  any  im- 
purities in  giving  color  to  the  glass.  Crown  glass  requires 
a  greater  heat  to  melt  its  ingredients,  than  those  kinds  which 
contain  a  larger  quantity  of  metallic  oxide,  especially  of  lead. 

Fritting. — After  the  materials  have  been  intimately  mixed, 
they  are  subjected  to  the  operation  c^We^  fritting.  This  con- 
sists in  exposing  them  to  a  dull  red  heat,  which  is  not  sufficient 
to  produce  their  fusion.  The  use  of  this  process  is  to  drive 
off  the  carbonic  acid,  and  other  gaseous  and  volatile  matters, 
which  would  otherwise  prove  troublesome  by  causing  the  ma- 
terials to  swell  up  in  the  glass  pots.  The  heat  is  gradually  in- 
creased, and  the  materials  constantly  stirred  for  some  hours, 
until  they  unite  into  a  soft,  adhesive  mass,  the  alkali  having 
gradually  combined  with  the  siliceous  earth.  The  reason  why 
the  fritting  is  conducted  at  a  low  heat,  is,  that  if  a  high  tem- 
perature were  applied  at  once,  the  alkali  would  be  driven  off, 
before  it  had  time  to  combine  with  the  silica. 

Melting. — The  homogeneous  mass,  ov  frit,  is  next  transfer- 
red to  the  glass  pots  of  the  melting  furnace.  These  are  cru- 
cibles made  of  the  most  refractory  clays  and  sand.  A  quantity 
of  old  glass  is  commonly  placed  upon  the  top  of  the  frit,  and 
the  heat  of  the  furnace  is  raised  to  its  greatest  height,  at  which 
state  it  is  continued  for  30  or  40  hours.  During  this  time  the 
materials  become  perfectly  united,  and  form  a  transparent, 
uniform  mass,  free  from  specks  and  bubbles.  The  whole  is 
then  suffered  to  cool  a  little,  by  slackening  the  heat  of  the  fur- 
nace, until  it  acquires  sufficient  tenacity  to  be  wrought. 


ARTS  OF  VITRIFICATION. 


451 


Blowing. — The  formation  of  window  glass  is  effected  by 
blowing  the  melted  matter,  or  metal,  as  it  is  called,  into  hollow 
spheres,  which  are  afterwards  made  to  expand  into  circular 
sheets.   The  workman  is  provided  with  a  long  iron  tube,  one  end 
of  which  he  thrusts  into  the  melted  glass,  turning  it  round  until 
a  certain  quantity  sufficient  for  the  purpose,  is  gathered,  or  ad- 
heres to  the  extremity.    The  tube  is  then  withdrawn  from  the 
furnace,  the  lump  of  glass,  which  adheres,  is  rolled  upon  a 
smooth  iron  table,  and  the  workman  blows  strongly  with  his 
mouth  through  the  tube.    The  glass,  in  consequence  of  its 
ductility,  is  gradually  inflated,  like  a  bladder,  and  is  prevented 
from  falling  off  by  a  rotary  motion  constantly  communicated  to 
the  tube.    The  inflation  is  assisted  by  the  heat,  which  causes 
the  air  and  moisture  of  the  breath  to  expand  with  great  power. 
Whenever  the  glass  becomes  so  stiff  from  coohng,  as  to  render 
the  inflation  difficult,  it  is  again  held  over  the  fire  to  soften  it, 
and  the  blowing  is  repeated  until  the  globe  is  expanded  to  the 
requisite  thinness.    It  is  then  received  by  another  workman, 
upon  an  iron  rod,*  while  the  blowing  iron  is  detached.    It  is 
now  opened  at  its  extremity,  and  by  means  of  the  centrifugal 
force  acquired  from  its  rapid  whirhng,  it  spreads  into  a  smooth 
uniform  sheet,  of  equal  thickness  throughout,  excepting  a 
prominence  at  the  centre,  where  the  iron  rod  was  attached. 

Annealing. — After  the  glass  has  received  the  shape  which 
it  is  to  retain,  it  is  transferred  to  a  hot  chamber,  or  annealing 
furnace,  in  which  its  temperature  is  gradually  reduced  until  it 
becomes  cold.  This  process  is  indispensable  to  the  durability 
of  glass,  for  if  it  is  cooled  too  suddenly,  it  becomes  extremely 
brittle,  and  flies  to  pieces  upon  the  slightest  touch  of  any  hard 
substance.  This  effect  is  shown  in  the  substances  called  Ru- 
pert^s  drops,  which  are  made  by  suddenly  cooling  drops  of 
green  glass,  by  letting  them  fall  into  cold  water.  These  drops 
fly  to  pieces  with  an  explosion,  whenever  their  smaller  extrem- 
ity is  broken  off.    The  Bologna  phials,  and  some  other  vessels 


^  Called  a  punt,  or  punting  iron. 


452 


ARTS  OF  VITRIFICATION. 


of  unannealed  glass,  break  into  a  thousand  pieces,  if  a  flint,  or 
other  hard  and  angular  substance,  is  dropped  into  them.  This 
phenomenon  seems  to  depend  upon  some  permanent  and  strong 
inequality  of  pressure,  for  when  these  drops  are  heated  so  red 
as  to  be  soft,  and  left  to  cool  gradually,  the  property  of  burst- 
ing is  lost,  and  the  specific  gravity  of  the  drop  is  increased. 

Broad  Glass. — This  is  a  coarser  kind  of  window  glass,  and 
is  made  from  sand  with  kelp  and  soap  boilers'  waste.  It  is 
blown  into  hollow  cones,  about  a  foot  in  diameter,  and  these, 
while  hot,  are  touched  on  one  side  with  a  cold  iron  dipped  in 
water.  This  produces  a  crack  which  runs  through  the  length 
of  the  cone,  nearly  in  a  right  line.  The  glass  then  expands 
into  a  sheet,  in  its  form,  resembling  somewhat  the  shape  of  a 
fan.  This  appears  to  have  been  one  of  the  oldest  methods  of 
manufacturing  glass. 

Flint  Glass. — Flint  glass,  so  called  from  its  having  been 
originally  made  of  pulverized  flints,  differs  from  window  glass, 
in  containing  a  large  quantity  of  the  red  oxide  of  lead. 
The  proportions  of  its  materials  differ,  but  in  round  numbers,  it 
consists  of  about  three  parts  of  fine  sand,  two  of  red  lead,  and 
one  of  pearl  ash,  with  small  quantities  of  nitre,  arsenic,  and 
manganese.  It  fuses  at  a  lower  temperature  than  crown  glass, 
has  a  beautiful  transparency,  a  great  refractive  power,  and  a 
comparative  softness,  which  enables  it  to  be  cut  and  polished 
with  ease.  On  this  account  it  is  much  used  for  glass  vessels 
of  every  description,  and  especially  those  which  are  intended 
to  be  ornamented  by  cutting.  It  is  also  employed  for  lenses, 
and  other  optical  glasses.  Flint  glass  is  worked  by  blowing, 
moulding,  pressing,  and  grinding.  Articles  of  complex  form, 
such  as  lamps  and  wine  glasses,  are  formed  in  pieces,  which 
are  afterwards  joined  by  simple  contact,  while  the  glass  is  hot. 
It  appears  that  the  red  lead  used  in  the  manufacture  of  flint 
glass,  gives  up  a  part  of  its  oxygen,  and  passes  to  the  state  of 
a  protoxide. 

Bottle  Glass. — Common  green  glass,  of  which  bottles  are 
made,  is  the  cheapest  kind,  and  formed  of  the  most  ordinary 


ARTS  OF  VITRIFICATION. 


453 


materials.  It  is  composed  of  sand  with  lime,  and  sometimes 
clay,  and  alkaline  ashes  of  any  kind,  such  as  kelp,  barilla,  or 
even  wood  ashes.  The  green  color  is  owing  to  the  impurities 
in  the  ashes,  but  chiefly  to  oxide  of  iron.  This  glass  is  hard, 
strong,  and  well  vitrified.  It  is  less  subject  to  corrosion  by 
strong  acids  than  flint  glass,  and  is  superior  to  any  cheap  mate- 
rial for  the  purposes  to  which  it  is  ordinarily  applied. 

Cylinder  Glass. — The  plates  of  crown  glass  which  are  ob- 
tained in  the  common  manner  by  blowing  them  in  circular 
plates,  afford  the  common  material  for  window  glass,  being  cut 
into  squares  by  first  marking  the  surface  deeply  with  a  diamond 
and  then  breaking  the  glass  in  the  same  direction,  the  crack 
always  following  the  exact  course  of  the  incision  made  by  the 
diamond.  But  there  is  always  a  loss  or  waste  in  cutting  squares 
from  a  circular  plate,  besides  which,  they  can  never  be  very 
large,  owing  to  the  protuberance,  or  hulVs  eye,  which  fills  the 
centre  of  the  plate,  so  that  a  square  can  never  be  larger  than 
can  be  described  within  less  than  half  the  circle.  To  remedy 
this  disadvantage,  plates  for  looking  glasses,  and  others  of  large 
size,  are  executed  in  a  different  way,  either  by  blowing  them 
in  cylinders,  or  by  casting  them  in  plates  at  first. 

Cylinder  glass  is  blown  at  first  in  spheres  hke  window  glass. 
These  are  elongated  into  spheroids  by  a  swinging  motion  which 
the  workman  gives  to  his  rod.  The  ends  of  this  spheroid  are 
successively  perforated,  thus  converting  it  into  an  irregular  cylin- 
der. One  side  of  this  cyhnder  is  cut  through  with  shears,  and 
the  glass  is  laid  upon  a  flat  surface,  where  it  expands  into 
a  uniform  plate,  without  any  protuberance.  It  is  then  annealed 
by  diminishing  the  heat  in  the  common  way.  When  the  plates 
are  intended  for  looking  glasses,  the  finest  materials  are  used, 
and  the  heat  kept  at  its  greatest  height  for  a  long  time,  to  dissi- 
pate all  impurities  and  remove  any  specks  or  bubbles. 

Plate  Glass. — Looking  glass  plates  may  be  blown  in  cylin- 
ders when  they  do  not  exceed  about  four  feet  in  length.  But 
they  cannot  well  be  blown  of  a  larger  size  than  this,  from  such 
a  quantity  of  glass  as  the  rod  will  take  up,  without  becoming 


454 


ARTS  OF  VITRIFICATION. 


too  thin  to  bear  polishing.  Plates,  however,  may  be  made  of 
more  than  double  this  size,  by  another  process  which  is  called 
casting,  and  which  is  the  only  mode  by  which  very  large  plates 
are  produced. 

When  glass  is  to  be  cast,  it  is  melted  in  great  quantities  in 
large  pots,  or  reservoirs,  until  it  is  in  a  state  of  perfect  fusion, 
in  which  state  it  is  kept  for  a  long  time.  It  is  then  drawn  out 
by  means  of  iron  cisterns  of  considerable  size,  which  are  low- 
ered into  the  furnace,  filled,  and  raised  out  by  machinery. 
The  glass  is  poured  out  from  these  cisterns,  upon  tables  of 
polished  copper  of  a  large  size,  having  a  rim  elevated  as  high 
as  the  intended  thickness  of  the  plate.  In  order  to  spread  it 
perfectly,  and  to  make  the  two  surfaces  parallel,  a  heavy  roller 
of  polished  copper,  weighing  500  pounds,  or  more,  is  rolled 
over  the  plate,  resting  upon  the  rim  at  the  edges.  The  glass, 
which  is  beginning  to  grow  stiff,  is  pressed  down  and  spread 
equally,  the  excess  being  driven  before  the  roller  till  it  falls  off 
at  the  extremity  of  the  table.  The  plate  is  then  ready  to  be 
annealed. 

As  the  plates  which  are  cast  for  looking  glasses  are  always 
uneven  and  dull  at  their  surface,  it  is  necessary  to  grind 
and  polish  them,  before  they  are  fit  for  use.  The  process  em- 
ployed for  producing  a  perfectly  even  and  smooth  surface,  is 
very  similar  to  that  employed  in  polishing  marble,  except  that 
the  glass  being  the  harder  substance,  requires  more  labor 
and  nicety  in  the  operation.  The  plate  to  be  polished  is  first 
cemented  to  a  table  of  wood,  or  stone,  with  plaster  of  Paris. 
A  quantity  of  wet  sand  or  emery  is  spread  upon  it,  and  an- 
other glass  plate  similarly  cemented  to  another  wooden  surface, 
is  brought  in  contact  with  it.  The  two  plates  are  then  rubbed 
together  until  the  surfaces  have  become  mutually  smooth  and 
plane.  The  emery  which  is  first  used  is  succeeded  by  emery 
of  a  finer  grain,  and  the  last  polish  is  given  by  colcothar, 
or  putty.  When  one  surface  has  become  perfectly  pohshed, 
the  cement  is  removed,  the  plate  turned,  and  the  opposite  side 
polished  in  the  same  manner. 


ARTS  OF  VITRIFICATION. 


465 


As  the  grinding  of  glass  causes  an  expenditure  of  a  consid- 
erable portion  of  its  substance,  a  great  waste  of  glass  takes 
place  when  foreign  materials  are  employed  in  the  manner  which 
has  been  described.  To  prevent  this  loss,  a  more  economical 
mode  has  been  introduced,  in  which  the  glass  is  ground  with 
pure  flint  reduced  to  powder.  The  mixture  of  glass  and 
flint,  which  is  left  after  the  operation,  is  valuable  for  forming 
fresh  glass. 

Moulding. — A  variety  of  ornamental  forms  are  produced 
upon  the  surface  of  glass  vessels,  by  impressions  given  to  them 
with  a  metallic  mould,  while  the  glass  is  in  a  hot  state.  Flint 
glass  is  the  kind,  which  is  used  for  articles  intended  to  possess 
much  brilliancy,  but  coarser  kinds,  even  of  colored  glass,  are 
also  subjected  to  the  same  process.  The  simplest  manner  in 
which  the  operation  is  conducted,  consists  in  blowing  the  glass 
into  the  mould,  till  it  receives  the  impression  on  its  outside. 
For  this  purpose  a  quantity  of  glass,  sufficient  to  form  the  in- 
tended vessel,  is  taken  up  on  the  end  of  a  pipe  and  inserted  at 
the  top  of  the  mould.  The  workman  then  blows  with  his 
mouth  till  a  hollow  portion  of  glass  is  driven  into  the  mould 
and  expands,  so  as  to  fill  every  part,  and  receive  an  impression 
on  its  outside.  The  mould  is  usually  made  of  copper,  with 
the  figure  cut  on  its  inside,  and  opens  with  hinges  to  permit 
the  glass  to  be  inserted,  and  taken  out.  As  the  mould  is 
of  necessity  much  colder  than  the  glass,  the  latter  substance 
is  chilled  at  its  surface,  as  soon  as  it  comes  in  contact  with  the 
copper;  hence  its  ductility  is  impaired,  and  the  impression 
given  is  never  so  sharp,  as  that  which  is  obtained  with  substan- 
ces, which  are  nearly  at  the  same  temperatures.  Moulded 
bottles,  phials,  decanters,  Sic.  are  made  in  this  way. 

Pressing. — An  improvement  has  been  made  in  the  process 
of  moulding  glass,  by  subjecting  the  material  to  pressure,  on 
the  inside  and  outside  at  the  same  time,  by  different  parts  of  a 
mould,  which  are  brought  suddenly  together  by  mechanical 
power.    This  process  has  been  carried  to  great  perfection  in 


456 


ARTS  OF  VITRIFICATION. 


several  of  the  manufactories  in  this  country,  *  and  produces 
specimens  which  compare  with  cut  glass  in  the  accuracy  and 
beauty  of  the  workmanship.  It  is  applied  only  to  solid  articles, 
and  to  vessels  which  are  not  contracted  at  top.  The  hot 
glass  being  dropped  into  the  mould,  a  part  called  the  follower, 
answering  to  the  inside  or  top  of  the  vessel,  or  other  article,  is 
immediately  pressed  down  upon  it  by  a  lever,  and  the  glass  is 
thus  stamped  with  a  very  distinct  impression  of  the  figure  on  both 
sides  at  once.  The  glass  vessel  is  sometimes  transferred  from 
the  mould  to  another  receptacle  called  the  receiver,  in  order  to 
preserve  its  shape  till  it  is  cool  enough  to  stand. 

Cutting. — The  name  of  cut  glass,  is  given  in  commerce  to 
glass  which  is  ground  and  polished  in  figures  with  smooth  sur- 
faces, appearing  as  if  cut  by  incisions  of  a  sharp  instrument. 
This  operation  is  chiefly  confined  to  flint  glass,  which,  being 
more  tough,  soft,  and  brilliant  than  the  other  kinds,  is  more 
easily  wrought,  and  produces  specimens  of  greater  lustre. 
An  establishment  for  cutting  glass  contains  a  great  number  of 
small  wheels  of  stone,  metal,  and  wood,  which  are  made  to 
revolve  rapidly  by  a  steam  engine,  or  other  power.  The  cut- 
ting of  the  glass  consists  entirely  in  grinding  away  successive 
portions,  by  holding  them  upon  the  surface  of  these  wheels. 
The  first,  or  rough  cutting,  is  sometimes  given  by  wheels  of 
stone,  resembling  grindstones.  Afterwards  wheels  of  iron  are 
used,  having  their  edges  covered  with  sharp  sand,  or  with 
emery  in  different  states  of  fineness.  The  last  polish  is  given 
by  brush  wheels  covered  with  putty,  which  is  an  oxide  of  tin 
and  lead.  To  prevent  the  friction  from  exciting  so  much 
heat  as  to  endanger  the  glass,  a  small  stream  of  water  continually 
drops  upon  the  surface  of  the  wheel. 

Stained  Glass. — The  name  of  staining  has  been  appHed  to 
the  process  by  which  painting  with  vitrifiable  colors,  is  execut- 
ed upon  the  surface  of  glass.  The  pigments  used  are  chiefly 
metallic  oxides,  which  do  not  exhibit  their  full  color,  until  they 

*  Particularly  at  Lechmere's  Point,  and  Sandwich. 


ARTS  OF  VITRIFICATION. 


457 


have  been  exposed  to  the  heat  of  the  furnace.  This  art  has 
been  repeatedly  described  as  being  no  longer  known  ;  but  this 
is  not  the  fact,  except  in  respect  to  some  particular  colors 
which  are  found  in  the  windows  of  the  ancient  cathedrals. 

The  metallic  oxides  used  in  staining  glass,  are  difficult  of 
fusion,  on  which  account  it  is  necessary  to  mix  them  with  a 
flux,  composed  of  glass,  with  lead  or  borax.  This  renders 
the  oxide  fusible  at  a  temperature,  which  does  not  injure  its 
color  ;  also  by  enveloping  the  particles,  it  causes  them  to  adhere 
to  the  glass,  and  afterwards  protects  them  from  the  atmosphere. 

A  very  beautiful  violet,  but  liable  to  turn  blue,  is  made  from 
a  flux  composed  of  borax  and  flint  glass  colored  with  one  sixth 
part  of  the  purple  of  Cassius,  precipitated  from  muriate  of 
gold  by  protomuriate  of  tin. 

A  fine  red  is  made  from  red  oxide  of  iron,  prepared  by 
nitric  acid  and  heat,  mixed  with  a  flux  of  borax  and  a  small 
proportion  of  red  lead. 

A  yellow,  equal  in  beauty  to  that  produced  by  the  ancients, 
may  be  made  from  muriate  of  silver,  oxide  of  zinc,  white 
clay,  and  the  yellow  oxide  of  iron,  mixed  together  without  any 
flux.  A  powder  remains  on  the  surface  after  the  glass  has 
been  baked,  but  this  is  easily  cleaned  off. 

Blue  is  produced  by  oxide  of  cobalt,  with  a  flux  composed 
of  fine  sand,  purified  pearl  ash,  and  red  lead. 

Black  is  produced  by  mixing  the  composition  for  blue,  with 
the  oxides  of  manganese  and  iron. 

To  stain  glass  green,  it  may  be  painted  blue  on  one  side, 
*  and  yellow  on  the  other. 

The  colors  ground  with  water  being  laid  upon  the  glass, 
must  be  exposed  to  heat  under  a  muffle,  so  as  to  be  heated 
equally  until  the  color  is  melted  upon  the  surface.  To  prevent 
the  panes  of  glass  from  bending,  they  are  placed  upon  a  bed 
of  bone  ashes,  of  quicklime, or  of  unglazed  porcelain.  Abed 
of  gypsum  has  been  recommended,  but  the  sulphuric  acid  ex- 
haling from  it  is  apt  to  injure  the  glass. 


58 


458 


ARTS  OF  VITRIFICATION. 


Among  ancient  specimens  of  painted  glass,  some  pieces 
have  been  found  in  which  the  colors  are  found  to  penetrate 
through  the  glass,  so  that  the  figure  appears  in  any  section 
made  parallel  to  the  surface.  It  is  supposed  that  such  pieces 
can  only  have  been  made  in  the  manner  of  mosaic,  by  accu- 
mulating transverse  filaments  of  glass  of  different  colors,  and 
uniting  them  by  heat,  the  process  being  one  of  great  labor. 
They  are  described  by  Winckelmann,  and  Caylus,  from  some 
specimens  brought  from  Rome. 

Enamelling. — Enamels  are  compositions  of  various  substan- 
ces which  when  vitrified  upon  the  surface  of  opaque  bodies, 
communicate  their  colors,  and  produce  the  effect  of  painting. 
Enamels  differ  from  stained  glass,  as  a  common  picture  differs 
from  a  transparency,  the  former  producing  its  effect  when 
viewed  by  reflected,  and  the  latter  by  transmitted  light.  En- 
amels are  executed  upon  the  surface  of  copper  and  other  me- 
tals, by  a  method  similar  to  painting.  One  coat,  or  color, 
often  requires  to  be  vitrified  before  another  is  laid  upon  it, 
and  thus  the  plate  to  be  enamelled  is  obliged  to  be  exposed 
to  heat  several  successive  times. 

Transparent  enamels  are  usually  rendered  opaque,  by  add- 
ing putty,  or  the  white  oxide  of  tin,  to  them.  The  basis  of  all 
enamels  is  therefore  a  transparent  and  fusible  glass.  The  ox- 
ide of  tin  renders  this  of  a  beautiful  white,  the  perfection  of 
which  is  greater  when  a  small  quantity  of  manganese  is  like- 
wise added.  If  the  oxide  of  tin  be  not  sufficient  to  destroy 
the  transparency  of  the  mixture,  it  produces  a  semiopaque 
glass,  resembling  the  opal. 

The  metals  employed  as  coloring  materials  are; — 1.  Gold. 
The  purple  of  Cassius  imparts  a  fine  ruby  tint.  2.  Silver. 
Oxide  or  phosphate  of  silver  gives  a  yellow  color.  3.  Iron. 
The  oxides  of  iron  produce  green,  yellow,  and  brown,  de- 
pending upon  the  state  of  oxidizement  and  quantity.  4.  Cop- 
per. The  oxides  of  copper  give  a  rich  green ;  they  also 
produce  a  red,  when  mixed  with  a  small  proportion  of  tartar, 
which  tends  partially  to  reduce  the  oxide.    5.  Antimony  im- 


ARTS  OF  VITRIFICATION. 


459 


parts  a  rich  yellow.  6.  Manganese.  The  black  oxide  of  this 
metal,  in  large  quantities,  forms  a  black  glass ;  in  smaller 
quantities,  various  shades  of  purple.  7.  Cobalt,  in  the  state 
of  oxide,  gives  beautiful  blues  of  various  shades  ;  and  with  the 
yellow  of  antimony,  or  lead,  it  produces  green.  8.  Chrome 
produces  fine  greens  and  reds,  depending  upon  its  state  of 
oxidizement. 

Artificial  Gems. — The  great  value  of  the  precious  stones 
has  led  to  artificial  imitations  of  their  color  and  lustre,  by  com- 
positions in  glass.  In  order  to  approximate  as  near  as  possible 
to  the  brilliancy  and  refractive  power  of  native  gems,  a  basis, 
called  a  paste,  is  made  from  the  finest  flint  glass,  composed  of 
selected  materials,  combined  in  different  proportions,  according 
to  the  preference  of  the  manufacturer.  This  is  mixed  with 
metallic  oxides  capable  of  producing  the  desired  color.  A 
great  number  of  complex  recipes  are  in  use  among  manufac- 
turers of  these  articles. 

Devitrification. — It  is  found  that  if  certain  kinds  of  glass  be 
exposed  to  heat  sufficient  to  keep  them  in  a  soft  state  for  some 
hours,  and  are  suffered  to  cool  gradually,  they  lose  their  trans- 
parency, and  pass  into  the  state  of  an  opaque  substance,  of  a 
greyish  white  color.  M.  Dartrigues,  *  who  has  examined  the 
cause  of  this  change,  asserts  that  it  is  owing  to  a  real  crystalli- 
zation of  the  vitreous  silicate.  Common  bottle  glass  is  most 
easily  changed  in  this  manner,  while  those  varieties  which 
contain  neither  lime  nor  alumina,  are  the  most  difficult  to  de- 
vitrify.  In  all  cases,  glass  which  has  undergone  this  change, 
requires  a  stronger  heat  to  melt  it  than  before. 

Reaumur^s  Porcelain. — It  has  been  frequently  observed  that 
during  the  annealing  of  green  glass,  some  parts  of  it  become 
white  and  opaque.  M.  Reaumur  made  experiments  on  this 
apparent  devitrification  of  glass,  and  found  it  was  owing  to  the 
alkali  flying  off  by  the  too  long  continuance,  or  too  great  de- 
gree of  the  heat,  and  that  the  opaque  changed  glass  had  ac- 

*  Journal  de  Physique,  1804. — Thenard,  Chimie,  ii.  473. 


460 


ARTS  OF  VITRIFICATION. 


quired  the  quality  of  bearing  sudden  transitions  of  heat  and 
cold  as  well  as  the  best  porcelain. 

For  the  purpose  of  making  vessels  of  this  kind,  common 
bottle  glass  is  chosen,  and  blown  into  the  proper  form.  The 
vessel  is  then  to  be  filled  to  the  top  with  a  mixture  of  white 
sand  and  gypsum,  and  is  set  in  a  large  crucible  upon  a 
quantity  of  the  same  mixture,  with  which  ^the  glass  vessels 
must  also  be  surrounded,  and  covered  over,  and  the  whole 
pressed  down  rather  hard.  The  crucible  is  then  to  be  covered 
with  a  lid,  the  junctures  well  luted,  and  put  into  a  potter's  kiln, 
where  it  remains  during  the  whole  time  that  the  pottery  is  bak- 
ing, after  which  the  glass  will  be  found  changed  into  a  milk 
white  porcelain. 

An  imitation  of  porcelain  which  is  lately  introduced  into  our 
shops,  and  which  combines  whiteness  with  a  beautiful  semi- 
transparency,  is  made  of  flint  glass,  containing  a  portion  of 
white  arsenic,  on  which  its  opacity  depends. 

Crystallo-Cerainie, — This  name  is  given  to  an  elegant,  but 
difficult,  species  of  manufacture,  in  which  medallions,  portraits, 
and  other  subjects  executed  in  an  opaque  material,  are  inclosed 
or  incrusted,  with  glass.  This  art  was  first  attempted  by  in- 
closing in  glass  small  figures  made  of  a  peculiar  kind  of  clay ; 
but  these  experiments  were  but  in  few  instances  successful, 
owing  to  the  unequal  expansion  and  contraction  of  the  two 
substances,  and  their  consequent  fracture.  More  recently  a 
composition  has  been  employed  for  the  opaque  figure,  which 
is  less  liable  to  these  accidents.  It  is  necessary  that  the  sub- 
stance employed  in  these  devices,  should  be  less  fusible  than 
glass,  incapable  of  generating  air,  and  at  the  same  time,  sus- 
ceptible of  expansion  and  contraction,  as  the  glass  becomes 
hot  or  cold.  The  ornamental  figures  are  introduced  into  the 
glass  while  hot,  and  thus  become  incorporated  with  it. 

Glass  Thread. — The  great  ductility  of  glass,  is  one  of 
its  most  remarkable  properties.  When  heated  to  a  sufficient 
degree,  it  may  not  only  be  moulded  into  any  possible  form 
with  the  utmost  facility,  but  it  can  be  drawn  out  into  the  finest 


ARTS  OF  VITRIFICATION. 


461 


fibres.  The  method  of  spinning  glass  is  very  simple.  The 
operator  holds  a  piece  of  glass  over  the  flame  of  a  lamp  with 
one  hand,  he  then  fixes  a  hook  to  the  melted  mass,  and  by 
withdrawing  it,  obtains  a  thread  of  glass  attached  to  the  hook. 
The  hook  is  then  fixed  in  the  circumference  of  a  cylindrical 
drum,  which  can  be  turned  round  by  the  hand ;  and  a  rapid 
rotary  motion  being  given  to  the  drum,  the  glass  is  drawn  in 
the  finest  threads  from  the  fluid  mass,  and  coiled  round  the 
cyhndrical  circumference.  M.  Reaumur  supposed,  with  great 
reason,  that  the  flexibihty  of  glass  increased  with  the  fine- 
ness of  the  threads,  and  he  therefore  conjectured,  that  if  they 
were  drawn  to  a  sufficient  degree  of  fineness,  they  might  be 
used  in  the  fabrication  of  stuffs.  He  succeeded  in  making 
them  as  fine  as  a  spider's  web,  but  he  was  never  able  to  obtain 
them  of  a  sufficient  length,  when  their  diameter  was  so  much 
reduced.  The  circumference  of  these  threads  is  generally  a 
flat  oval,  about  three  or  four  times  as  broad  as  it  is  thick.  By 
using  opaque  and  transparent  glass,  of  different  colors,  artists 
have  been  able  to  produce  many  beautiful  ornaments. 

Remarks. — Pure  glass  possesses  the  remarkable  property  of 
suffering  no  change  by  the  application  of  an  intense  heat. 
The  effect  of  great  heats  is  only  to  melt  the  glass,  or  to  dissi- 
pate it  in  vapor  ;  but  as  long  as  any  of  the  glass  remains,  it  still 
preserves  its  transparency,  and  other  distinguishing  properties. 

Of  all  the  solid  substances  whose  expansibihty  has  been  ac- 
curately examined,  glass  possesses  the  property  of  being  least 
affected  by  heat  or  cold.  Its  expansion,  according  to  General 
Roy,  with  an  increase  of  heat  equal  to  180  degrees  of  Fahren- 
heit's thermometer,  is  only  0.000776,  while  that  of  platina  is 
0.000856,  and  that  of  hammered  zinc,  0.00301 1.  On  account 
of  this  property,  glass  is  peculiarly  fitted  for  containing  fluids 
whose  expansions  are  under  examination,  as  its  own  change  of 
form  may  in  ordinary  cases  be  neglected.  For  the  same  reason 
it  is  better  than  any  other  substance  for  the  simple  pendulum 
of  a  clock. 


462 


ARTS  OF  VITRIFICATION. 


The  invention  of  glass  seems  to  have  been  extremely  ancient, 
and  imperfect  specimens  are  found  in  the  sarcophagi  of  Egyp- 
tian mummies.  Glass  windows  appear  not  to  have  been  in  use 
among  the  Romans  of  the  Augustan  age  ;  though  vessels  and 
plates  of  glass,  are  found  at  Herculaneum  and  Pompeii.  Most 
of  the  important  improvements  in  the  manufacture  of  this  sub- 
stance, have  been  made  by  the  moderns. 


Parkes's  Chemical  Essays,  8vo.  vol.  ii. ; — Loysel,  Essai  sur  VArt 
de  la  Verrerie,  8vo.  1800 ; — Brogniart,  Art  de  VEmaiUeur,  Annates 
de  Chimie,  torn.  ix.  and  other  works ; — Franklin  Journal,  v.  80  ; — Article 
Glass  in  Rees'  Cyclopedia,  and  in  the  Edinburgh  Encyclopedia ; — 
Chaptal,  Chimit  Appliquee  aux  Arts,  4  vols,  8vo.  1806; — Gray's 
Operative  Chemist,  8vo.  1828; — Thenard,  Traite  de  Chimin,  vol.  ii. ; — 
Brande's  Chemistry; — Beckman's  History  of  Inventions,  4  vols,  8vo. 
translated  1797; — Works  of  Neri,  Blancourt,  Kunckel,  Reaumur, 
&c. 


CHAPTER  XX. 


ARTS  OF  INDURATION  BY  HEAT. 

Common  clay,  with  its  varieties,  consisting  essentially  o( 
alumina  and  silica ;  also  the  artificial  imitations  of  clay,  into 
which  these  earths  enter,  possess  properties  adapted  to  render 
them  highly  useful  in  the  arts.  When  mixed  with  water,  they 
form  a  ductile  and  tenacious  paste,  capable  of  being  moulded 
into  various  forms,  and  of  acquiring,  when  exposed  to  the  heat 
of  a  furnace,  a  durable  and  stony  hardness.  These  com- 
pounds are  used  in  different  states,  to  form  the  materials  both 
for  the  largest  structures,  and  the  most  delicate  ornaments ; 
and  they  are  surpassed  by  few  substances  in  the  power  of 
resisting  the  effects  of  exposure  and  time.  Bricks,  tiles,  terra 
cotta,  pottery,  and  porcelain,  are  the  most  noticeable  products 
of  the  branch  of  industry,  in  the  operations  of  which  indurated 
clay  is  the  material. 

Bricks. — The  use  of  bricks  in  building,  may  be  traced  to 
the  earliest  ages,  and  they  are  found  among  the  ruins  of  almost 
every  ancient  nation.  The  w^alls  of  Babylon,  some  of  the  an- 
cient structures  of  Egypt  and  Persia,  the  walls  of  Athens,  the 
Rotunda  of  the  Pantheon,  the  temple  of  Peace,  and  the  Ther- 
mae, at  Rome,  were  all  of  brick.  The  earhest  bricks  were 
dried  in  the  sun,  and  were  never  exposed  to  great  heat,  as  ap- 
pears from  the  fact  that  they  contain  reeds  and  straws,  upon 
which  no  mark  of  burning  is  visible.  These  bricks  owe  their 
preservation  to  the  extreme  dryness  of  the  climate  in  which 
they  have  remained,  since  the  earth  of  which  they  are  made, 
often  crumbles  to  pieces  when  immersed  in  water,  after  having 
kept  hs  shape  for  more  than  two  thousand  years.  This  is  the 
case  with  some  of  the  Babylonian  bricks,  with  inscriptions  in 


464 


ARTS  OF  INDURATION  BY  HEAT. 


the  arrow  headed  character,  which  have  been  brought  to  this 
country.  The  ancients,  however,  at  a  later  period,  burnt  their 
bricks,  and  it  is  these  chiefly  which  remain  at  the  present  day. 
The  antique  bricks  were  larger  than  those  employed  by  the 
moderns,  and  were  almost  universally  of  a  square  form.  Be- 
sides bricks  made  of  clay,  the  ancients  also  employed  a  kind 
of  factitious  stone,  composed  of  a  calcareous  mortar.* 

Modern  bricks  receive  their  hardness  from  exposure  to  heat 
in  the  process  of  burning.  The  common  clay  of  which  they 
are  made,  consists  of  a  mixture  of  argillaceous  earth  and  sand. 
Most  of  our  common  clays  contain  also  oxide  of  iron,  which 
causes  the  bricks  to  turn  red  in  burning.  Pure  clays  become 
white  in  the  furnace,  such  as  that  of  which  pipes  are  made, 
and  common  crockery  ware.  Clay,  after  it  is  taken  from  the 
earth,  requires  to  be  thoroughly  mixed,  incorporated,  and  mel- 
lowed, before  it  is  fit  for  the  manufacture  of  bricks.  For  this 
purpose,  it  is  to  be  dug  in  the  summer,  or  fall,  and  exposed  to 
the  influence  of  the  frost  through  the  winter.  It  should  be 
worked  over  repeatedly  with  the  spade,  and  not  made  into 
bricks  till  the  ensuing  spring,  previously  to  which,  it  is  well 
tempered,  either  by  treading  it  with  oxen,  or  by  a  horse  mill, 
till  it  is  reduced  to  a  tough,  homogeneous  paste.  In  propor- 
tion to  the  labor  bestowed  on  this  process,  the  bricks  become 
solid,  hard,  and  strong.  The  clay,  after  being  thus  prepared, 
is  forced  into  moulds  to  receive  the  shape  of  bricks,  and  after- 
wards dried  in  the  sun. 

Pressed  bricks,  which  are  used  to  form  the  facing  of  walls 
in  the  better  kinds  of  structures,  are  finished  in  a  machine. 
The  roughness  and  change  of  form  to  which  common  bricks 
are  liable,  is  owing  in  part  to  the  evaporation  of  a  portion  of 
the  water  which  the  clay  contains.  To  remedy  the  difficulty 
arising  from  this  cause,  the  bricks  after  being  moulded  in  the 
common  manner,  are  exposed  to  the  sun  till  they  are  nearly 
dried,  retaining,  however,  sufficient  plasticity  to  be  still  capable 

*Somc  travellers  have  even  advanced  an  opinion  that  the  Pyramids  of 
£gypt  are  constructed  with  an  artificial  stone. 


ARTS  OF  INDURATION  BY  HEAT. 


465 


of  a  slight  change  of  form.  In  this  state  they  are  placed  in 
an  iron  mould  and  subjected  to  a  strong  pressure,  by  which 
they  become  regular  in  shape,  and  very  smooth.  A  machine 
usually  contains  a  number  of  moulds  arranged  in  a  circle,  or 
otherwise,  so  that  the  power  is  applied  to  them  in  succession, 
and  the  bricks  pressed  with  rapidity. 

The  burning  of  bricks  is  commonly  performed  in  this  coun- 
try, by  forming  them  into  large  square  piles,  denominated 
clamps,  or  with  us,  kilns,  having  flues  or  cavities  at  the  bottom 
for  the  insertion  of  the  fuel,  and  interstices  between  the  bricks 
for  the  fire  and  hot  air  to  penetrate.  A  fire  is  kindled  in  these 
cavities,  and  gradually  increased  for  the  first  twelve  hours,  after 
which  it  it  is  kept  up  at  a  uniform  height  for  several  days  and 
nights,  till  the  bricks  are  sufficiently  burned.  Much  care  and 
experience  are  necessary  in  regulating  the  fire,  since  too  much 
heat  vitrifies  them,  and  too  little  leaves  them  soft  and  friable. 
In  some  places  the  burning  of  bricks  is  conducted  in  permanent 
kilns  erected  for  the  purpose. 

Tiles. — Tiles  are  plates  of  burnt  clay,  resembling  bricks  in 
their  composition,  and  manufacture,  and  used  for  the  covering 
of  roofs.  They  are  necessarily  made  thicker  than  slates  or 
shingles,  and  thus  impose  a  greater  weight  upon  the  roofs. 
Their  tendency  to  absorb  water,  promotes  the  decay  of  the 
wood  work  beneath  them.  Tiles  are  usually  shaped  in  such  a 
manner  that  the  edge  of  one  tile  receives  the  edge  of  that  next 
to  it,  so  that  water  cannot  percolate  between  them.*  Tiles, 
both  of  burnt  clay  and  marble,  were  used  by  the  ancients,  and 
the  former  continue  to  be  employed  in  various  parts  of  Europe. 
Floors  made  of  flat  tiles  are  used  in  many  countries,  particu- 
larly in  Italy. 

Terra  Cotta. — The  Italian  name  terra  cotta,  in  French 
terre  cuite,  in  its  most  general  sense,  implies  clay  indurated  by 
heat.  In  the  arts,  however,  its  use  seems  to  be  restricted  to 
the  finer  clays,  in  which  ornamental  designs  have  been  execut- 

*  For  different  forms  of  tiles  used  at  Florence,  Trieste,  &c,  see  Cadell's 
Journey  in  Italy  and  Carniola,  Plate  X. 
59 


466 


ARTS  OF  INDURATION  BY  HEAT. 


ed,  both  by  the  ancients  and  moderns.  Not  only  vases,  but 
imitations  of  sculpture,  and  architectural  decorations,  are  suc- 
cessfully made  from  this  material.  Among  other  things,  a 
complete  restoration  of  the  Choragic  monument  of  Lysicrates, 
at  Athens,  has  been  made  from  terra  cotta  in  the  court  of  the 
Louvre,  at  Paris.  From  the  facility  with  which  it  is  moulded 
into  any  form,  this  substance  would  be  of  great  use  in  archi- 
tecture, were  it  not  for  the  unequal  shrinking  of  the  clay  from 
heat,  and  the  difficulty  of  preserving  accurately  the  original 
proportions. 

Crucibles. — Crucibles,  melting  pots,  and  other  vessels  in- 
tended for  use  in  the  furnace,  require  to  be  made  of  substances 
which  sustain  a  high  temperature  without  fusion.  When  they 
are  made  of  about  one  part  of  pure  clay,  mixed  with  three  of 
sand,  and  slowly  dried  and  annealed,  they  are  found  to  bear  a 
great  heat,  and  will  retain  most  of  the  metals  which  are  melted 
for  use  in  the  arts.  Such  crucibles,  however,  are  liable  to  be 
acted  upon,  and  destroyed  at  high  temperatures,  if  the  metals 
are  suffered  to  become  oxidized,  or  if  saline  fluxes  are  used. 
To  prevent  this  accident,  some  crucibles  are  made  entirely  of 
clay,  which  is  burnt,  coarsely  powdered,  and  mixed  with  fresh 
clay.  These  are  found  very  refractory  in  the  furnace.  Cru- 
cibles are  also  made  of  plain  Stourbridge  clay,  of  Wedgewood's 
ware,  of  graphite,  and  of  platina. 

Pottery. — In  manufactures  of  vessels  from  argillaceous 
compounds,  the  different  degrees  of  beauty  and  cosdiness  de- 
pend upon  the  quality  of  the  raw  material  used,  and  upon  the 
labor  and  skill  expended  in  the  operation.  The  cheapest 
products  of  the  art,  are  those  made  of  common  clay,  similar 
to  that  of  which  bricks  are  formed,  and  which,  from  the  iron  it 
contains,  usually  turns  red  in  burning.  Next  to  this  is  the 
common  crockery  ware,  formed  of  the  purer  and  whiter  clays 
in  which  iron  exists  only  in  minute  quanthies.  Porcelain, 
which  is  the  most  beautiful  and  expensive  of  all,  is  formed 
only  from  argillaceous  minerals  of  extreme  delicacy,  united 
with  siliceous  earths  capable  of  communicating  to  them  a  semi- 
transparency,  by  means  of  its  vitrification. 


ARTS  OF  INDURATION  BY  UK  AT. 


467 


Clay,  altliough  it  is  a  compound  body,  and  possesses  more 
silica  than  alumina,  nevertheless  derives  characters  from  the 
latter,  which  abundantly  distinguish  it  from  minerals  which  are 
more  purely  siliceous.  The  processes  of  its  manufacture 
are  in  most  respects  the  reverse  of  those  applied  to  glass,  that 
substance  being  softened  by  heat,  and  wrought  at  a  high  tem- 
perature, whereas  the  clay  is  wrought  while  cold,  and  after- 
wards hardened  by  heat. 

Operations. — Though  the  various  kinds  of  pottery  and 
porcelain,  differ  from  each  other  in  the  details  of  their  manu- 
facture, yet  there  are  certain  general  principles  and  processes 
which  are  common  to  them  all.  The  first  belongs  to  the  pre- 
paration of  the  clay,  and  consists  in  dividing  and  washing  it, 
till  it  acquires  the  requisite  fineness.  The  quality  of  the  clay 
requires  by  the  intermixture  of  a  certain  proportion  of  siliceous 
earth,  the  effect  of  which  is  to  increase  hs  firmness,  and 
render  it  less  liable  to  shrink  and  crack,  on  exposure  to  heat. 
In  common  clay,  a  sufficient  quantity  of  sand  exists  in  a  state 
of  natural  mixture,  to  answer  this  purpose.  But  in  the  finer 
kinds,  an  artificial  admixture  of  silica  is  necessary.  The 
paste  which  is  thus  formed,  is  thoroughly  beaten  and  kneaded 
to  render  it  ductile,  and  to  drive  out  the  air.  It  is  then  ready 
to  receive  its  form.  The  form  of  the  vessel  intended  to  be 
made,  is  given  to  the  clay  either  by  turning  it  on  a  wheel,  or 
by  casting  it  in  a  mould.  When  dry  it  is  transferred  to  the 
oven  or  furnace,  and  there  burnt  till  it  acquires  a  sufficient  de- 
gree of  hardness  for  use.  Since,  how^ever,  the  clay  is  still 
porous,  and  of  course  penetrable  to  w^ater,  it  is  necessary  to 
glaze  it.  This  is  done  by  covering  the  surface  with  some  vit- 
rifiable  substance,  and  exposing  it  a  second  time  to  heat,  until 
this  substance  is  converted  into  a  coating  of  glass. 

In  the  coarse  earthen  ware,'which  is  made  of  common  clay, 
the  clay,  after  being  mixed  and  kneaded  until  it  has  acquired 
the  proper  ductility,  is  transferred  to  a  sort  of  revolving  table, 
called  the  wheel.  A  piece  of  clay  of  sufficient  size,  being 
placed  in  the  centre  of  this  table,  a  rotary  motion  is  communi- 


468 


ARTS  OF  INDURATION  BY  HEAT. 


cated  to  it  by  the  feet.  The  potter  then  begins  to  shape  it 
with  his  hands,  which  are  previously  wet  to  prevent  its  adher- 
ing to  the  fingers.  The  rotary  motion  gives  it  a  circular  form 
and  it  is  gradually  wrought  up  to  the  intended  shape,  a  tool 
being  occasionally  used  to  assist  the  finishing.  The  vessels 
are  now  set  aside  to  dry,  after  which  they  are  baked  in  the 
oven,  or  kiln.  The  glazing  of  this  kind  of  pottery  is  given  by 
metallic  oxides,  which  vitrify  at  a  low  heat.  A  yellow  glaz- 
ing is  communicated  by  the  oxide  of  lead,  black  by  the  oxide 
of  manganese,  and  white  by  the  oxide  of  tin.  Unglazed  ware 
is  porous  and  permeable  to  water,  as  is  seen  in  common  flower 
pots  and  coolers. 

Stone  Ware. — The  kinds  of  pottery  denominated  stone 
ware,  may  be  formed  of  the  clays  which  are  used  for  other  ves- 
sels, by  applying  to  them  a  much  greater  degree  of  heat,  the 
effect  of  which  is  to  increase  very  much  their  strength  and 
solidity.  These  vessels  do  not  require  to  be  glazed  with  any 
metallic  oxides,  but  afford  the  material  of  their  own  glazing  by 
a  vitrification  of  their  surface.  When  the  furnace  in  which 
they  are  burnt  has  arrived  at  its  greatest  heat,  a  quantity  of 
muriate  of  soda,  or  common  salt,  is  thrown  into  the  body  of 
the  kiln.  The  salt  rises  in  vapor  and  envelopes  the  hot  ware, 
and  by  the  combination  of  its  alkali  with  the  siliceous  particles 
on  the  surface  of  the  ware,  a  perfect  vitrification  is  produced. 
This  glazing,  consisting  of  an  earthy  glass,  is  insoluble  in  most 
chemical  agents,  and  is  free  from  the  objections  to  which  ves- 
sels glazed  with  lead  are  liable,  that  of  communicating  an  un- 
wholesome quality  to  liquids  contained  in  them,  by  the  solution 
of  the  lead  in  common  acids,  which  they  frequently  contain. 

White  Ware. — The  better  sorts  of  earthen  ware  are  made 
of  white  clay,  or  of  clay  containing  so  little  oxide  of  iron  that 
it  does  not  turn  red  in  burning,  but  on  the  contrary,  improves 
its  whiteness  in  the  furnace.  This  kind,  commonly  called 
pipe  clay,  is  found  very  pure  in  Devonshire  and  Dorsetshire,  in 
England.  In  the  manufactory  of  Mr  Wedge  wood,  to  whose 
industry  and  ingenuity,  the  public  are  indebted  for  some  of  the 


ARTS  OF  INDURATION  BY  HEAT. 


469 


finest  specimens  of  the  art,  the  clay  is  prepared  by  first 
bringing  it  to  a  state  of  minute  division,  by  the  aid  of  machin- 
ery. This  machinery  consists  of  a  series  of  iron  blades  or 
knives  fixed  to  an  upright  axis,  and  made  to  revolve  in  a  cy- 
linder, and  intersecting  or  passing  between  another  set  of 
blades  which  are  fixed  to  the  cylinder.  The  clay,  by  the 
continual  intersection  of  these  blades,  is  minutely  divided,  and 
when  sufficiently  fine,  is  transferred  to  a  vat.  It  is  here  agitat- 
ed with  water  until  it  assumes  the  consistence  of  a  pulp,  so 
thin,  that  the  coarser  or  stony  particles  can  subside  to  the  bot- 
tom after  a  little  rest,  while  the  finer  clay  remains  in  suspension. 
This  last  is  poured  off  and  suffered  to  subside,  after  which  it 
is  passed  through  sieves  of  difterent  fineness,  and  becomes 
sufficiently  attenuated  for  use. 

To  this  clay  is  added  a  certain  quantity  of  flint  reduced  to 
powder  by  heating  it  red  hot,  and  throwing  it  into  cold  water 
to  diminish  the  cohesion  of  its  parts.  Afterwards  it  is  pounded 
by  machinery,  ground  in  a  mill,  sifted  and  washed  precisely  as 
the  clay  is  treated,  and  made  into  a  similar  pulp.  In  this  state 
the  two  ingredients  are  intimately  mixed  together  in  such 
quantities  that  the  clay  bears  to  the  flint  the  proportion  of  about 
five  to  one. 

The  object  of  adding  flint  to  the  clay,  is  twofold.  It  lessens 
the  shrinking  of  the  clay  in  the  fire,  and  thus  renders  it  less 
liable  to  warp  and  crack  in  the  burning.  At  the  same  time, 
by  its  partial  fusion,  it  communicates  to  the  ware  that  beautiful 
translucency  which  is  so  much  admired  in  porcelain,  and  of 
which  the  simple  clay  wares  are  destitute. 

The  fine  pulp  of  flint  and  clay  being  intimately  mixed,  is 
then  exposed  to  evaporation  by  a  gentle  heat,  until  the  super- 
fluous water  is  dissipated  and  the  mass  reduced  to  a  proper 
consistency  to  work.  To  produce  a  uniformity  in  the  thick- 
ness of  the  material,  it  is  taken  out  in  successive  pieces  which 
are  repeatedly  divided,  struck,  and  pressed  together,  till  every 
part  becomes  blended  with  the  rest. 


470 


ARTS  OF  INDURATION  BY  HEAT. 


Throwing. — The  formation  of  circular  vessels  is  done  by 
the  process  called  throwing,  performed  on  the  potter's  wheel, 
in  the  manner  already  described,  except  that  in  large  manufac- 
tories the  wheel  is  not  turned  by  the  operator  himself,  but  by 
an  assistant,  or  a  steam  engine.  The  handles  and  similar  ap- 
pendages, are  made  by  forcing  the  clay  with  a  piston,  through 
an  aperture  of  the  size  and  shape  which  it  is  desired  to  pro- 
duce. When  formed,  the  handles  are  cemented  to  the  ware 
by  a  thin  mixture  of  the  clay  with  water,  which  the  workmen 
call  slip.  The  vessels,  when  complete,  are  dried  with  a  grad- 
ual heat,  in  a  room  heated  to  SO  or  90  degrees,  and  after  be- 
ing smoothed  from  any  irregularities  of  surface,  they  are  con- 
veyed to  the  kiln. 

Pressing. — The  only  vessels  which  can  be  made  in  the 
wheel  or  lathe,  are  those  of  a  circular  form.  When  the  form 
is  different,  the  vessel  must  be  made  either  by  press  work  or 
casting.  The  press  work  is  executed  in  moulds  made  of 
plaster  of  Paris,  one  half  the  figure  being  on  one  side  of  the 
mould  and  the  other  half  on  the  other  side.  These  fit  accu- 
rately together.  The  clay  is  first  made  into  two  flat  pieces  of 
the  thickness  of  the  articles  ;  one  of  these  is  pressed  into  one 
side  of  the  mould,  and  the  other  into  the  other  side.  The 
superfluous  clay  being  cut  away,  the  two  sides  of  the  mould 
are  brought  together  to  unite  the  two  halves  of  the  vessel. 
The  mould  is  now  separated  from  the  clay,  and  the  article  is 
finished  as  to  form.  When  dry,  it  is  completed  by  the  addi- 
tion of  handles,  or  other  parts  belonging  to  it.  All  vessels  of 
an  oval  form,  or  which  have  flat  sides,  may  be  made  in  this 
way. 

Casting. — In  the  third  method  called  casting,  the  clay  is 
used  in  the  state  of  pulp,  sufficiently  thin  to  flow.  It  is  poured 
into  moulds  made  of  plaster,  by  which  the  superfluous  water 
being  rapidly  absorbed,  the  clay  is  deposited,  and  acquires 
sufficient  solidity  to  preserve  the  shape  communicated  by  the 
mould.  It  is  then  taken  out  and  dried,  and  transferred  to  the 
kiln. 


ARTS  OF  INDURATION  BY  HEAT. 


471 


Burning. — All  vessels,  when  formed,  are  in  a  very  tender 
and  frangible  state,  before  they  are  submitted  to  the  ac- 
tion of  fire.  The  burning,  or  hardening,  is  performed  in  kilns, 
and  to  preserve  the  ware  from  injury,  it  is  inclosed  in  cases,  or 
boxes,  of  burnt  clay,  called  saggars,  in  which  it  is  heated  red 
hot,  by  the  flame  circulating  among  the  cases.  The  fire  is 
kept  up  from  24  to  48  hours,  and  the  saggars  suffered  to  cool 
before  they  are  removed.  The  ware  is  then  found  to  have 
acquired  great  hardness,  and  is  converted  into  a  dry,  sonorous, 
and  extremely  bibulous  solid.  In  this  state  it  is  called  the 
biscuit.  It  adheres  strongly  to  the  tongue,  and  absorbs  water 
in  such  quantities,  that  vessels  in  this  state  are  used  as  coolers, 
being  kept  saturated  with  water,  which,  as  it  passes  constantly 
to  the  outer  surface,  generates  cold  by  its  evaporation. 

Printing. — When  colors,  or  designs,  are  to  be  impressed 
upon  the  vessels,  it  is  necessary  in  most  cases,  that  it  should 
be  done  before  the  ware  is  glazed.  In  China,  the  drawings 
on  the  surface  of  porcelain,  and  other  wares,  are  executed  by 
hand,  with  the  pencil,  and  the  same  method  is  pursued  in 
Europe,  in  elaborate  pieces  of  workmanship.  But  in  the 
common  figured  white  ware,  the  designs  are  first  engraved  upon 
copper,  and  an  impression  taken  on  thin  paper,  in  the  common 
mode  of  copperplate  printing,  except  that  the  color  is  a  me- 
tallic oxide.  The  paper  is  then  moistened,  applied  closely 
to  the  biscuit,  and  rubbed  on,  by  which  process  the  coloring 
matter  is  absorbed,  in  consequence  of  the  porosity  of  the 
earthen  material.  The  paper  is  then  washed  off,  leaving  the 
printed  figure  transferred  to  the  sides  of  the  vessel.  Blue  and 
white  ware  is  printed  with  oxide  of  cobalt,  and  a  black  color 
is  imparted  by  an  admixture  with  the  oxides  of  manganese 
and  iron. 

Glazing. — To  prevent  the  penetration  of  fluids,  it  is  neces- 
sary that  vessels  should  be  glazed,  or  covered,  with  a  vitreous 

*  Mr  Parkes  informs  us  that  such  improvements  are  made  in  the  manufac- 
ture of  this  article,  that  the  Chinese  potters  are  now  supplied  from  England, 
witl)  all  the  cobalt  they  consume. 


472 


ARTS  OF  INDURATION  BY  HEAT. 


coating.  The  materials  of  common  glass  would  afford  the 
most  perfect  glazing  to  crockery  ware,  were  it  not  that  the  ra- 
tio of  its  expansion  and  contraction  is  not  the  same  with  that 
of  the  clay,  so  that  a  glazing  of  this  sort  is  liable  to  cracks 
and  fissures,  when  exposed  to  changes  of  temperature.  A 
mixture  of  equal  parts  of  oxide  of  lead  and  ground  flints  is 
found  to  be  a  durable  glaze  for  the  common  cream  colored 
ware,  and  is  generally  used  for  that  purpose.  These  materials 
are  first  ground  to  an  extremely  fine  powder,  and  mixed  with 
water  to  form  a  thin  liquid.  The  ware  is  dipped  into  this  fluid 
and  drawn  out.  The  moisture  is  soon  absorbed  by  the  clay, 
leaving  the  glazing  particles  upon  the  surface.  These  are  af- 
terwards melted  by  the  heat  of  the  kiln,  and  constitute  a  uni- 
form and  durable  vitreous  coating. 

The  English  and  French  manufacturers  find  it  necessary  to 
harden  their  vessels  by  heat,  or  bring  them  to  the  state  of  bis- 
cuit, before  they  are  glazed ;  but  the  composition  used  by  the 
Chinese,  resists  water,  after  it  has  been  once  dried  in  the  air, 
so  as  to  bear  dipping  in  the  glazing  liquid,  without  injury.  This 
gives  them  a  great  advantage  in  the  economy  of  fuel. 

China  Ware. — The  Chinese  porcelain  excels  other  kinds 
of  ware,  in  the  delicacy  of  its  texture,  and  the  partial  trans- 
parency which  it  exhibits  when  held  against  the  light.  It  has 
been  long  known  and  manufactured  by  the  Chinese,  but  has 
never  been  successfully  imitated  in  Europe,  until  within  the 
last  century.  In  China,  porcelain  is  made  by  the  union  of 
two  earths,  to  which  they  give  the  name  of  petuntze  and  kaolin, 
the  former  of  which  is  fusible  in  the  furnace,  the  latter  not. 
Both  these  earths  are  varieties  of  feldspar,  the  kaolin  being 
feldspar  in  a  state  of  decomposition,  and  which  is  rendered  in- 
fusible by  having  lost  the  small  quantity  of  potass  which  origi- 
nally entered  into  its  composition.  The  Petuntze  is  feldspar 
undecomposed.  These  earths  are  reduced  to  an  impalpable 
powder,  by  processes  similar  to  those  already  described,  and  in- 
timately blended  together.  When  exposed  to  a  strong  heat  the 
petuntze  partially  melts  and  enveloping  the  infusible  kaolin  com- 


ARTS  OP  INDURATION  BY  HEAT. 


473 


municates  to  it  a  fine  semitransparency.  The  glazing  is  pro- 
duced by  the  petuntze  alone,  applied  in  minute  powder  to  the 
ware,  after  it  is  dry. 

European  Porcelain. -^S'mce  the  nature  of  the  Chinese 
earths  has  been  understood,  materials  nearly  of  the  same  kind, 
have  been  found  in  different  parts  of  Europe,  and  the  manu- 
facture of  porcelain  has  been  carried  on  in  several  countries, 
but  particularly  at  Sevres,  in  France,  with  great  success.  The 
European  porcelains,  in  the  elegance  and  variety  of  their  forms 
and  the  beauty  of  the  designs  which  are  executed  upon  them, 
excel  the  manufactures  of  the  Chinese.  But  the  Oriental 
porcelain  has  not  yet  been  equalled  in  hardness,  strength, 
durability,  and  the  permanency  of  its  glaze.  Several  of  the 
processes  which  are  successfully  practised  by  the  Chinese,  re- 
main still  to  be  learnt  by  Europeans.  The  manufacturers  in 
Saxony,  are  said  to  have  approached  most  nearly  in  their  pro-  - 
ducts,  to  the  character  of  the  Asiatic  porcelain. 

The  porcelain  earths  are  found  in  various  parts  of  the  United 
States,  and  will  doubtless  hereafter  constitute  the  material  of 
important  manufactures. 

The  finer  and  more  costly  kinds  of  porcelain,  derive  their 
value,  not  so  much  from  the  quality  of  their  material,  as  from 
the  labor  bestowed  on  their  external  decoration.  When  the 
pieces  are  separately  painted  by  hand,  with  devices  of  different 
subjects,  their  value,  as  specimens  of  art,  depends  upon  the 
size  of  the  piece,  the  number  and  brilliancy  of  the  colors  em- 
ployed, and  more  especially  upon  the  skill  and  finish,  exhibited 
by  the  artist  in  the  design.  The  manual  part  of  the  operation 
consists  in  mixing  the  coloring  oxide  with  a  fluid  medium, 
commonly  an  essential  oil,  and  applying  it  with  camels'  hair 
pencils.  The  colors  used  are  the  same  as  those  employed  in 
other  kinds  of  enamelling.  When  one  color  requires  to  be 
laid  over  another,  this  is  performed  by  a  second  operation  ;  and 
it  often  happens  that  a  piece  of  porcelain  has  to  go  into  the 
enamel  kiln,  four  or  five  times,  when  a  great  variety  of  colors 
is  contained  in  the  painting. 
60 


474 


ARTS  OF  INDURATION  BY  HEAT. 


Gilding  upon  porcelain  is  performed  by  applying  the  gold 
after  its  solution  in  nitro-nnuriatic  acid,  ground  up  with  oil  of 
turpentine,  and  mixed  with  a  flux.  When  exposed  to  heat, 
the  oxygen,  if  any  is  present,  escapes,  and  a  coating  of  metal- 
lic gold  remains  fixed  to  the  porcelain.  This  has  at  first  the 
appearance  of  dead  gold,  but  is  subsequently  burnished  with  an 
instrument  of  polished  steel,  or  with  an  agate,  or  blood  stone. 

The  articles  called  lustre  ware,  are  of  two  kinds.  The  first 
of  these,  called  gold  lustre^,  is  made  of  red  clay,  and  is  brush- 
ed over  with  a  thin  coating  of  gold  obtained  from  its  solution 
in  nitro-muriatic  acid,  the  acid  being  driven  off  by  heat.  The 
other  kind  is  called  silver  lustre^  and  is  made  of  the  cream- 
colored  ware,  covered  in  the  same  manner  with  a  film  of  pla- 
tinum. 

Etruscan  Vases, — -This  name  is  given  to  a  kind  of  painted 
antique  vases,  of  great  beauty,  lightness,  and  dehcacy,  which 
are  dug  up  in  the  graves  of  lower  Italy.  Many  of  them  are 
supposed  to  be  of  Grecian,  and  not  of  Etruscan  origin.  Some 
of  these  vases  are  entirely  black,  and  in  this  case  there  is  no 
separate  glazing,  but  the  interior  of  the  mass  has  the  same  ap- 
pearance with  the  outside.  Other  vases  are  furnished  with  a 
simple  black  coating,  but  unlike  the  modern  glazing.  It  appears 
from  analysis,  that  this  black  color  is  produced  by  a  carbona- 
ceous substance,  perhaps  bitumen ;  but  the  art  of  applying  it  is 
unknown  to  the  moderns. 

The  celebrated  Portland  vase,  discovered  in  the  tomb  of 
Alexander  Severus,  and  for  which  the  Dutchess  of  Portland 
paid  a  thousand  guineas,  is  said  to  be  made,  not  of  porcelain, 
but  of  glass.  The  body  of  the  urn  consists  of  a  deep  blue 
glass,  over  which  is  applied  a  coating  of  white  semitransparent 
glass.  The  white  covering  appears  to  have  been  cut  away  by 
the  lapidary,  in  the  same  way  as  the  subjects  of  antique  cameos 
on  colored  grounds.  Mr  Wedgewood,  at  a  great  expense, 
produced  imitations  of  this  vase  in  porcelain. 

Among  the  curiosities  of  this  art,  may  be  mentioned  the 
magic  'porcelain  of  the  Chinese.    The  figures  upon  the  sur- 


ARTS  OF  INDURATION  BY  HEAT. 


475 


face  of  this  ware,  are  executed  in  such  a  manner  that  they  are 
said  to  be  invisible  when  the  vessels  are  empty,  *  but  become 
apparent  when  the  vessels  are  filled  with  water. 

*  See  the  article  Porcelain,  in  the  Edinburgh  Encyclopedia,  ascribed  to  M. 
Brogniart. 


Parke s's  Chemical  Essays,  vol.  ii. ; — Rees'  Cyclopedia  and  Edin- 
burgh Encyclopedia,  articles  Pottery,  Porcelain,  &c.; — Chaptal, 
Chimin  Appliquie  aux  Ms,  torn,  iii.; — Gray's  Operative  Chemist, 
8vo.  1828. 


CHAPTER  XXL 


ON  THE  PRESERVATION  OF  ORGANIC  SUBSTANCES. 

Decomposition. — The  compounds  which  are  spontaneously 
formed  by  organic  bodies,  both  vegetable  and  animal,  are  of  a 
different  nature  from  those  which  exist  in  unorganized  matter. 
They  are  the  peculiar  results  of  vital  processes,  and  neither 
their  structure  nor  composition,  can  be  imitated  by  art.  Dur- 
ing life,  the  elements  of  organic  bodies  are  held  together  by 
vital  affinities,  under  the  influence  of  which  they  were  originally 
combined.  But  no  sooner  does  life  cease,  than  these  elements 
become  subject  to  the  laws  of  inert  matter.  The  original  af- 
finities, which  had  been  modified,  or  suspended,  during  life, 
are  brought  into  operation  ;  the  elementary  atoms  react  upon 
each  other,  new  combinations  are  formed,  and  the  organized 
structure  passes  sooner  or  later  into  decay. 

The  rapidity  with  which  decomposition  takes  place  in  or- 
ganic bodies,  depends  upon  the  nature  of  the  particular  sub- 
stance, and  upon  the  circumstances  under  which  it  is  placed. 
Temperature,  moisture,  and  the  presence  of  decomposing 
agents,  greatly  afiect  both  the  period,  and  extent  of  this  pro- 
cess. By  regulating,  or  preventing,  the  operation  of  these 
causes,  the  duration  of  most  substances  may  be  prolonged,  and 
many  materials  are  rendered  useful,  which,  if  left  to  themselves, 
w^ould  be  perishable  and  worthless.  The  preservation  of  tim- 
ber, of  fibrous  substances,  of  leather,  of  food,  and  of  various 
objects  of  art,  are  subjects  of  the  highest  importance,  and  have 
received,  at  various  times,  much  attention  from  scientific  ex- 
perimentalists. 

Temperature. — The  influence  of  temperature,  in  accelerat- 
ing, or  retarding,  the  decoy  of  organized  substances,  is  generally 


ON  THE  PRESERVATION  OF  ORGANIC  SUBSTANCES.  477 


known.  Cold  tends  to  check  the  progress  of  destructive  fer- 
mentation, and  when  it  extends  so  far  as  to  produce  congela- 
tion, its  preservative  power  is  complete.  Bodies  of  men  and 
animals  have  been  found  frozen,  in  situations  where  they  had 
remained  for  years,  and  even  ages ;  and  the  recent  discovery 
of  an  elephant  in  the  ice  of  Siberia,  shows  that  the  period  of 
this  preservation  is  unlimited.  On  the  other  hand,  in  warm 
seasons  and  in  hot  climates,  everything  tends  to  corruption  and 
decay.  Both  animal  and  vegetable  substances,  pass  rapidly 
into  the  putrefactive  fermentation ;  alimentary  substances  are 
difficult  to  preserve,  and  when  moisture  is  combined  with  heat, 
ships,  houses,  and  other  structures  of  wood,  as  well  as  cordage, 
canvass,  and  clothing,  have  the  period  of  their  duration  greatly 
abridged. 

Dryness. — Although  certain  degrees  of  heat,  especially 
when  combined  with  moisture,  tend  greatly  to  promote  decom- 
position, yet  if  the  degree  of  heat,  and  the  circumstances  under 
which  it  acts,  are  such  as  to  produce  a  perfect  dissipation  of 
moisture,  the  further  progress  of  decay  is  arrested.    The  exer- 
tion of  chemical  affinities  usually  requires  that  one  of  the  agents 
at  least  should  be  in  a  fluid  state.    And  while  a  body  is  in  a 
state  of  perfect  dryness,  no  internal  chemical  change  is  likely 
to  befall  it.    The  beams  and  furniture  of  houses,  often  remain 
entire  for  centuries.    In  the  arid  caverns  of  Egypt,  the  wood 
of  sarcophagi  appears  to  have  undergone  no  alteration  in  the 
lapse  of  two  or  three  thousand  years,  the  fibres  of  linen  tex- 
tures are  found  distinct  and  perfect,  though  weakened  in 
strength,  and  the  dried  flesh  of  the  mummies  themselves  dis- 
cover no  marks  of  decomposition.    In  cabinets  of  Natural 
History,  the  specimens,  so  long  as  they  are  kept  perfectly  dry, 
undergo  no  alteration  from  spontaneous  de^iay.    They  are, 
however,  extremely  liable  to  the  depredations  of  insects,  from 
which  they  require  to  be  protected,  either  by  impregnating 
them  with  poisonous  substances,  or  by  inclosing  them  in  cases 
which  are  hermetically  tight. 


478 


ON  THE  PRESERVATION 


Wetness. — Some  materials,  especially  wood,  are  capable  of 
lasting  for  a  long  time,  if  kept  continually  immersed  in  water, 
especially  at  low  temperatures.  Thus  the  lower  part  of  a 
pump  log  is  much  more  durable  than  the  upper,  if  kept  always 
under  water.  The  effect  of  pure  water  is  to  dissolve  and  car- 
ry off  the  soluble  parts,  leaving  the  fibrous  structure  in  a  state 
less  liable  to  fermentation  than  before.  Some  animal  substan- 
ces, likewise,  such  as  leather,  bear  immersion  in  water  for  a 
considerable  time.  It  must  be  observed,  however,  that  the 
effect  of  wetness  upon  most  organized  bodies,  is  to  soften  their 
texture,  and  render  them  less  able  to  support  mechanical  vio- 
lence, than  when  dry.  Wood,  after  having  been  long  immers- 
ed, if  taken  out  and  dried,  is  found  to  be  more  brittle  than 
it  was  before. 

But  the  state  which  most  rapidly  prom.otes  decay,  is  that  of 
alternate  moisture  and  dryness,  attended  with  exposure  to  the 
atmospheric  air.  It  appears  in  regard  to  wood,  that  in  each 
wetting,  a  sensible  portion  of  substance  is  dissolved,  and  that 
in  each  drying,  a  new  portion  of  soluble  matter  is  formed.  In 
a  ship,  under  common  circumstances,  the  parts  which  first  de- 
cay, are  those  which  are  situated  between  wind  and  water,  or 
are  subjected  to  alternate  dryness  and  moisture.  So  also  in  a 
post  standing  in  the  earth,  the  part  which  first  decays,  is  usually 
that  which  is  nearest  the  surface  of  the  ground.  Exposure  to 
the  vicissitudes  of  weather,  is  also  one  of  the  most  common 
and  active  causes  of  decomposition. 

Antiseptics. — A  certain  class  of  substances  has  received  the 
name  of  antiseptics,  from  their  power,  when  present,  of  resist- 
ing putrefaction  in  organic  bodies,  as  well  as  in  their  products. 
Such  are  charcoal,  tannin,  resins,  camphor,  bitumen,  sugar,  chlo- 
rine, alcohol,  oils,  acids,  and  salts  of  various  kinds.  The  man- 
ner in  which  they  exert  their  preservative  agency,  is  not  fully 
understood.  It  appears,  however,  that  in  some  cases  they  com- 
bine with  the  substance  to  be  preserved,  forming  a  less  perisha- 
ble compound,  as  in  the  instance  of  leather;  and  probably  in 
other  instances  they  unite  with  and  qualify  the  decomposing 
agents,  which  are  present. 


OF  ORGANIC  SUBSTANCES. 


479 


Timber. — A  vast  expense  is  every  year  created  by  the  pre- 
mature decay  of  wood,  employed  in  ships  and  other  structures, 
which  are  exposed  to  vicissitudes  of  weather,  and  especially  if 
they  are  subjected  to  the  influence  of  warmth  combined  with 
moisture.  Trees  of  different  species,  vary  greatly  in  the  du- 
rability of  their  wood,  yet  none  of  the  species  commonly  em- 
ployed, are  capable  of  withstanding  for  many  years,  the  effect 
of  unfavorable  exposures  and  situations.  The  decay  of  tim- 
ber is  sometimes  superficial,  and  sometimes  internal.  In  the 
former  case,  the  outside  of  the  wood  first  perishes  and  crum- 
bles away,  and  successive  strata  are  decomposed,  before  the 
internal  parts  become  unsound.  In  the  other  species,  which 
is  distinguished  by  the  name  of  the  dry  rot,  the  disease  begins 
in  the  interior  substance  of  the  wood,  particularly  of  that  which 
has  not  been  well  seasoned,  and  spreads  outwardly,  causing 
the  whole  mass  to  swell,  crack,  and  exhale  a  musty  odor. 
Different  fungous  vegetables  sprout  out  of  its  substance,  the 
wood  loses  its  strength,  and  crumbles  finally  into  a  mass  of 
dust.  This  disease  prevails  most  in  a  warm,  moist,  and  con- 
fined atmosphere,  such  as  frequently  exists  in  the  interior  of 
ships,  and  in  the  cellars  and  foundations  of  houses.  Its  de- 
structive effects  in  ships  of  v\^ar,  have  given  rise  of  late  to  nu- 
merous publications.  Some  writers  consider  that  the  dry  rot 
is  not  essentially  different  from  the  more  common  kinds  of  de- 
cay, but  there  seems  to  be  sufficient  reason  for  the  distinction 
which  has  usually  been  drawn.  The  prevention  of  the  evil 
has  been  attempted  in  various  ways,  and  with  some  degree  of 
success. 

Felling. — It  is  agreed  by  most  writers  that  the  sap 
of  vegetables  is  the  great  cause  of  their  fermentation  and  de- 
cay. Hence  it  appears  desirable,  if  there  is  any  season,  in 
which  the  trunk  of  a  tree  is  less  charged  with  sap  than  at  oth- 
ers, that  this  time  should  be  selected  for  felling  it.  The  mid- 
dle of  summer  and  the  middle  of  winter,  are  undoubtedly  the 
periods  when  the  wood  contains  least  sap.  In  the  months  of 
spring  and  fall,  in  which  the  roots  prepare  sap,  but  no  leaves 


480 


ON  THE  PRESERVATION 


exist  to  expend  it,  the  trunk  is  overcharged  with  sap  ;  and  in 
many  trees,  as  the  maple  and  birch,  sap  will  flow  out  at  these 
seasons,  if  the  trunk  is  wounded.  In  summer,  on  the  contrary, 
when  the  leaves  are  out,  the  sap  is  rapidly  expended,  and  in 
winter,  when  the  roots  are  dormant,  it  is  sparingly  produced  ; 
so  that  no  surplus  of  this  fluid  apparently  exists.  From  rea- 
soning a  priori,  it  would  seem  that  no  treatment  would  be  so 
effectual  in  getting  rid  of  the  greatest  quantity  of  sap,  as  to  gir- 
dle the  tree,  by  cutting  away  a  ring  of  alburnum,  in  the  early 
part  of  summer,  thus  putting  a  stop  to  the  further  ascent  of  the 
sap,  and  then  to  suffer  it  to  stand  until  the  leaves  should  have 
expended,  by  their  growth,  or  transpiration,  all  the  fluid  which 
could  be  extracted  by  them  previously  to  the  death  of  the  tree.* 
The  wood  would  thus  probably  be  found  in  the  driest  state  to 
which  any  treatment  could  reduce  it  in  the  living  state.  BufFon 
has  recommended  stripping  the  trees  of  their  bark  in  spring, 
and  felling  them  in  the  subsequent  fall.  This  method  is  said 
to  harden  the  alburnum,  but  the  cause  is  not  very  apparent,  nor 
is  the  success  at  all  certain. 

Seasoning. — At  whatever  period  timber  is  felled,  it  requires 
to  be  thoroughly  seasoned,  before  it  is  fit  for  the  purposes  of 
carpentry.  The  object  of  seasoning  is  partly  to  evaporate  as 
much  of  the  sap  as  possible,  and  thus  to  prevent  its  influence 
in  causing  decomposition  ;  and  partly  to  reduce  the  dimensions 
of  the  wood,  so  that  it  may  be  used  without  inconvenience 
from  its  further  shrinking.  Timber  seasons  best,  when  placed 
in  dry  situations,  where  the  air  has  a  free  circulation  round  it. 
Gradual  drying  is  considered  a  better  preservative  of  wood, 
than  a  sudden  exposure  to  warmth,  even  of  the  sun,  for  warmth 
abruptly  applied,  causes  cracks  and  flaws  from  the  sudden  and 
unequal  expansion  produced  in  different  parts.  Two  or  three 
years'  seasoning  is  requisite  to  produce  tightness  and  durability 
in  the  wood  work  of  buildings.  It  must  be  observed  that  sea- 
soning in  the  common  way,  only  removes  a  portion  of  the  aqueous 


See  Mc William  on  the  Dry  Rot,  pages  151,  and  158. 


OF  ORGANIC  SUBSTANCES. 


481 


and  volatile  matter  from  the  wood.  The  extractive,  and  oth- 
er soluble  portions,  still  remain,  and  are  liable  to  ferment,  though 
in  a  less  degree,  whenever  the  wood  reabsorbs  moisture.  Such, 
indeed,  is  the  force  of  capillary  attraction,  that  wood,  exposed 
to  the  atmosphere  in  our  climate,  never  gives  up  all  its  moisture. 

Preservation  of  Tlmhcr. — When  wood  is  to  be  kept  in  a 
dry  situation,  as  in  the  interior  of  houses,  no  other  preparation 
is  necessary  than  that  of  thorough  seasoning.  But  when  it  is 
to  be  exposed  to  the  vicissitudes  of  weather,  and  still  more 
when  it  is  to  remain  in  a  warm  and  moist  atmosphere,  its  pre- 
servation often  becomes  extremely  difficult.  Numerous  ex- 
periments have  been  made,  and  many  volumes  written,  upon 
the  preservation  of  timber,  and  the  prevention  of  the  dry  rot ; 
but  the  subject  is  not  yet  brought  to  a  satisfactory  conclusion. 
The  methods  which  have  hitherto  been  found  most  successful, 
consist  in  extracting  the  sap,  in  excluding  moisture,  and  in  im- 
pregnating the  vessels  of  the  wood  with  antiseptic  substances. 

For  extracting  the  sap,  the  process  of  water  seasoning  is 
recommended.  It  consists  in  immersing  the  green  timber  in 
clear  water  for  about  two  weeks,  after  which  it  is  taken  out 
and  seasoned  in  the  usual  manner.  A  great  part  of  the  sap, 
together  with  the  soluble  and  fermentable  matter,  is  said  to  be 
dissolved  or  removed,  by  this  process.  Running  water  is  more 
effectual  than  that  which  is  stagnant.  It  is  necessary  that  the 
timber  should  be  sunk,  so  as  to  be  completely  under  water, 
since  nothing  is  more  destructive  to  wood,  than  partial  immer- 
sion. Mr  Langton*  has  proposed  to  extract  the  sap  by  means 
of  an  air  pump,  the  timber  being  inclosed  in  tight  cases,  with  a 
temperature  somewhat  elevated,  and  the  sap  being  discharged 
in  vapor  by  the  operation  of  the  pump. 

It  appears  extremely  probable,  that  if  trees  were  felled  in 
summer,  and  the  huts  immediately  placed  in  water  without  re- 
moving the  branches,  a  great  part  of  their  sap  would  be  ex- 
pended by  the  vegetative  process  alone,  and  replaced  by  water^ 
It  is  well  known  that  branches  of  plants,  if  inserted  in  water^ 
*  Repertory  of  Arts,  1826.    Franklin  Journal,  ii.  and  vi 

61 


482 


ON  THE  PRESERVATION 


continue  for  some  days,  to  grow,  to  transpire,  and  to  perform 
their  other  functions.  This  they  probably  do  at  the  expense 
of  the  sap,  or  assimilated  fluid,  which  was  previously  in  them, 
while  they  replace  it  by  the  water  they  consume.  This  state 
of  things  continues  until  the  juices  are  too  far  diluted  to  be 
capable  of  any  longer  sustaining  life. 

The  charring  of  timber  by  scorching,  or  burning  its  outside, 
is  commonly  supposed  to  increase  its  durability,  but  on  this 
subject  the  results  of  experiment  do  not  agree.  Charcoal  is 
one  of  the  most  durable  of  vegetahle  substances,  but  the  con- 
version of  the  surface  of  wood  into  charcoal,  does  not  neces- 
sarily alter  the  character  of  the  interior  part.  As  far,  however, 
as  it  may  operate  in  excluding  worms,  and  arresting  the  spread- 
ing of  an  infectious  decay,  like  the  dry  rot,  it  is  useful.  Prob- 
ably also,  the  pyroligneous  acid  which  is  generated  when  wood 
is  burnt,  may  exert  a  preservative  influence. 

The  exclusion  of  moisture  by  covering  the  surface  with  a 
coating  of  paint,  varnish,  tar,  &£c.,  is  a  well  known  preservative 
of  wood  which  is  exposed  to  the  weather.  If  care  is  taken 
to  renew  the  coat  of  paint,  as  often  as  it  decays,  wood  on  the 
outside  of  buildings,  is  sometimes  made  to  last  for  centuries. 
But  painting  is  no  preservative  against  the  internal,  or  dry  rot. 
On  the  contrary,  when  this  disease  is  begun,  the  effect  of  paint, 
by  choking  the  pores  of  the  wood,  and  preventing  the  exhala- 
tion of  vapors  and  gases  which  are  formed,  tends  rather  to  ex- 
pedite, than  prevent  the  progress  of  decay.  Paint  itself  is 
rendered  more  durable,  by  covering  it  with  a  coating  of  fine 
sand.  Wood  should  never  be  painted,  which  is  not  thoroughly 
seasoned. 

The  impregnation  of  wood  with  tar,  bitumen,  and  other  re- 
sinous substances,  undoubtedly  promotes  its  preservation.  It 
is  the  opinion  of  some  writers,  *  that  *  woods  abounding  in  re- 
sinous matter,  cannot  be  more  durable  than  others, '  but  the 
reverse  of  this  is  proved  every  year  in  the  pine  forests  of  this 

*  Tredgold's  Elementary  Principles  of  Carpentry,  page  166. 


OF  ORGANIC  SUBSTANCES. 


483 


country,  where  the  lightwood,  as  it  is  called,  consisting  of  the 
knots  and  other  resinous  parts  of  pine  trees,  remains  entire, 
and  is  collected  for  the  purpose  of  affording  tar,  long  after  the 
remaining  wood  of  the  tree  has  decayed.  A  coating  of  tar  or 
turpentine,  externally  applied  to  seasoned  timber,  answers  the 
same  purpose  as  paint  in  protecting  the  wood,  if  it  is  renewed 
with  sufficient  frequency.  Wood  impregnated  with  drying  oils, 
such  as  linseed  oil,  becomes  harder,  and  more  capable  of  re- 
sisting moisture.  It  is  frequently  the  custom,  in  this  country, 
to  bore  a  perpendicular  hole  in  the  top  of  a  mast,  and  fill  it 
with  oil.  This  fluid  is  gradually  absorbed  by  the  vessels  of 
the  wood,  and  penetrates  the  mast  to  a  great  distance.  Ani- 
mal oils,  in  general,  are  less  proper  for  this  purpose,  being 
more  liable  to  decomposition. 

The  preservative  quality  of  common  salt  (muriate  of  soda), 
is  well  known.  An  example  of  its  effect  is  seen  in  the  hay  of 
salt  marshes,  which  is  frequently  housed  before  it  is  dry,  and 
which  often  becomes  damp  afterwards  from  the  deliquescence 
of  its  salt,  yet  remains  unchanged  for  an  indefinite  length 
of  time.  In  the  salt  mines  of  Poland  and  Hungary, 
the  galleries  are  supported  by  wooden  pillars,  which  are 
found  to  last  unimpaired  for  ages,  in  consequence  of  being 
impregnated  with  the  salt,  while  pillars  of  brick  and  stone, 
used  for  the  same  purpose,  crumble  away  in  a  short  time  by 
the  decay  of  their  mortar.  Wooden  piles  driven  into  the  mud 
of  salt  flats  and  marshes,  last  for  an  unlimited  time,  and  are 
used  for  the  foundations  of  brick  and  stone  edifices.  In  canals 
which  have  been  made  in  the  salt  marshes  about  Boston,  and 
other  places,  trunks  of  oak  trees  are  frequently  found  with  the 
heart  wood  entire  and  fresh,  at  a  depth  of  five  or  six  feet  below 
the  surface.  At  Medford,  (Mass.)  the  stumps  of  trees  are  found 
standing  in  the  gravelly  bottom  of  the  salt  marsh  where  the 
tide  rises  in  the  canals  four  or  five  feet  above  them.  This 
bottom  must  originally  have  constituted  the  surface  of  the 
ground,  and  must  have  settled  long  enough  ago  for  the  marsh 
mud  to  have  accumulated,  as  it  has  done  for  miles  round,  ap- 
parently since  that  period. 


484 


ON  THE  PRESERVATION 


The  application  of  salt  in  minute  quantities,  is  said  rather  to 
hasten,  than  prevent  the  decay  of  vegetable  and  animal  bodies. 
Yet  the  practice  of  docking  timber,  by  immersing  it  for  some 
time  in  sea  water,  after  it  has  been  seasoned,  is  generally  ad- 
mitted to  promote  its  durability.  There  are  some  experiments 
which  appear  to  show,  that  after  the  dry  rot  has  commenced, 
immersion  in  salt  water  effectually  checks  its  progress,  and 
preserves  the  remainder  of  the  timber.  *  In  some  of  the 
public  ships  built  in  the  United  States,  the  interstices  between 
the  timbers  in  various  parts  of  the  hull,  are  filled  with  dry  salt. 
When  this  salt  deliquesces,  it  fills  the  pores  of  the  wood  with 
a  strong  saline  impregnation,  but  it  has  been  said,  m  some  cases, 
to  render  the  inside  of  the  vessel  uncomfortably  damp.  If 
timber  is  immersed  in  a  brine  made  of  pure  muriate  of  soda, 
without  the  bitter  deliquescent  salts,  which  sea  water  contains, 
the  evil  of  dampness  is  avoided. 

A  variety  of  other  substances  besides  common  salt,  act  as 
antiseptics  in  preventing  the  dry  rot,  and  the  growth  of  the 
fungus  which  attends  it.  Nitre  and  alum  have  been  recom- 
mended for  this  purpose,  and  some  of  the  metallic  salts  are 
considered  still  more  effectual.  Of  these  the  sulphates  of  iron, 
copper,  and  zinc,  have  the  effect  to  harden  and  preserve  the 
timber.  Wood  boiled  in  a  solution  of  the  former  of  these, 
and  afterwards  kept  some  days  in  a  warm  place  to  dry,  is  said 
to  become  impervious  to  moisture.  Corrosive  sublimate, 
which  is  recommended  by  Sir  H.  Davy,  is  a  powerful  preser- 
vative of  organized  substances  from  decay,  and  proves  destruc- 
tive to  parasitic  vegetables  and  animals ;  but  hs  safety,  in  regard 
to  the  health  of  crews  if  used  in  large  quantities  about  the  wood 
of  a  ship,  may  be  considered  as  doubtful. 

*  The  British  frigate  Resistance,  which  went  down  in  Malta  harbor,  and 
the  Eden,  which  was  sunk  in  Plyraoutli  Sound,  were  both  affected  with  dry 
rot.  These  ships,  after  remaining  many  months  under  water,  were  raised, 
and  it  was  found  that  the  disease  was  wholly  arrested.  Every  vestige  of 
funo;us  had  disappeared,  and  the  ships  remained  in  service  afterwards,  per- 
fectly sound  from  any  further  decay.  Supplement  to  the  Encyclopedia  Bri- 
tannica,  iii.  682. 


OF  ORGANIC  SUBSTANCES. 


485 


An  opinion  has  been  supported  in  this  country,  thattlie  decay 
of  timber  in  ships,  by  dry  rot,  is  owing  to  the  impure  atmos- 
pheric generated  by  bilge  water,  and  that  it  is  to  be  remedied 
by  constructing  ships  with  a  view  to  their  free  and  effectual 
ventilation.  ^' 

Preservation  of  Animal  Textures. — The  solid  and  fibrous 
portions  of  organic  bodies,  such  as  wood,  bone,  shell,  horn, 
hair,  cotton,  &£c.,  are  most  easy  of  preservation.  But  the 
soft  and  succulent  parts,  such  as  the  pulp  of  vegetables,  and 
the  flesh  of  animals,  are  extremely  perishable,  owing  to  the 
decomposing  influence  of  their  fluid  contents  ;  and  require  the 
assistance  of  art  to  communicate  to  them  any  degree  of  dura- 
bility. These  substances,  when  they  cannot  be  dried,  are  usu- 
ally preserved  by  enveloping,  or  impregnating  them  with  anti- 
septics. For  alimentary  substances  the  antiseptics  used  are 
sugar,  alcohol,  salt,  and  the  acetous  and  pyroligneous  acids ; 
while  for  scientific  specimens  and  preparations,  alcohol,  oil  of 
turpentine,  resinous  and  bituminous  varnishes,  alum  and  corro- 
sive sublimate,  are  found  most  effectual. 

Embalming. — As  the  art  of  embalming  can  hardly  be  rank- 
ed among  the  useful  arts,  any  further  than  it  can  be  made  sub- 
servient to  the  promotion  of  anatomy,  or  natural  history,  it  is 
not  much  cultivated  at  the  present  day.  The  ancient  Egyp- 
tians converted  the  dead  bodies  of  their  friends  into  mummies, 
by  removing  the  viscera  from  the  large  cavities  and  replacing 
them  with  aromatic,  saline,  and  bituminous  substances,  particu- 
larly asphaltum ;  and  also  enveloping  the  outside  of  the  body 
in  cloths  impregnated  with  similar  materials.  These  impreg- 
nations prevented  decomposition,  and  excluded  insects,  until 
perfect  dryness  look  place.  In  times  comparatively  modern, 
embalming  has  been  practised  with  great  success,  particularly 
where  bodies  have  remained  at  a  low  and  uniform  temperature, 
and  have  been  protected  from  the  access  of  the  air.  The 
body  of  king  Edward  the.  First,  of  England,  appears  upon 

*  See  a  pamphlet  on  Dry  Rot  by  Commodore  Barron,  Norfolk,  182S. 


486 


ON  THE  PRESERVATION 


record  to  have  been  embalmed.  He  died  in  July,  1307,  and 
was  buried  in  Westminster  Abbey.  In  1770,  his  tomb  was 
opened,  and  the  contents  examined,  and  after  this  lapse  of  463 
years,  the  body  of  the  monarch  remained  entire.  The  flesh 
upon  the  face  was  a  little  wasted,  but  not  putrid.  The  body 
of  Canute,  king  of  Denmark,  who  invaded  England  in  1017, 
was  found  very  fresh  in  1776,  by  the  workmen  employed  in 
repairing  Winchester  Cathedral.  The  bodies  of  William  the 
Conqueror,  and  of  Matilda  his  wife,  both  buried  at  Caen,  were 
found  entire  in  the  sixteenth  century.  In  like  manner,  the  re- 
mains of  various  other  princes,  and  persons  of  note,  have 
been  discovered  to  be  undecayed,  some  centuries  after  their 
decease.  In  certain  cases,  bodies  not  embalmed  have  been 
preserved,  merely  by  the  exclusion  of  air,  and  a  uniform  low 
temperature. 

But  the  most  perfect  of  all  the  modes  of  preserving  the 
animal  body,  without  continued  immersion,  appears  to  be  a 
thorough  impregnation  with  corrosive  sublimate.  This  may 
be  performed,  by  saturating  the  soft  solids  with  a  strong  solu- 
tion, consisting  of  about  four  ounces  of  bichloride  of  mercury 
to  a  pint  of  alcohol.  This  is  injected  into  the  blood  vessels, 
and  after  the  viscera  are  removed,  the  whole  body  is  immersed 
for  three  months  in  the  same  solution.  At  the  end  of  this  pe- 
riod it  easily  dries,  and  is  afterwards  nearly  imperishable.  * 

In  what  are  called  by  anatomists  wet  preparations^  the  ob- 
jects are  kept  immersed  in  alcohol,  and  last  for  an  indefinite 
time.  Oil  of  turpentine  answers  the  same  purpose,  and  in  the 
Museum  of  Natural  History,  in  Paris,  there  is  a  head  prepared 
in  this  way,  more  than  a  hundred  years  ago,  by  the  celebrated 
Ruytch,  which  preserves  all  the  vivacity  of  its  colors.  In  cold 
weather  the  liquid  becomes  opaque,  but  is  again  rendered 
transparent  in  the  spring. 

Tanning. — The  skins  of  animals,  when  prepared  by  merely 
drying  them,  are  stift',  incapable  of  resisting  water,  and  liable 

*  Sec  a  paper  by  Dr  J.  C.  Warren,  on  Embalming,  in  the  Boston  Journal 
of  Arts,  vol.  i.  p.  269. 


OF  ORGANIC  SUBSTANCES. 


487 


to  decay.  If,  however,  they  are  impregnaled  with  tlie  tannin 
which  is  found  in  astringent  vegetables,  that  substance  combines 
with  the  gelatin  of  the  skin,  and  forms  a  durable  compound, 
which  is  no  longer  soluble  in  water.  Common  tanned  leather 
is  prepared  in  this  way.  The  skins  are  previously  prepared 
by  soaking  them  in  lime  water,  which  facilitates  the  separation 
of  the  cuticle  and  hair.  A  slight  degree  of  putrescency  assists 
the  sarne  object.  They  are  then  immersed  in  the  tan  pits,  in 
a  strong  infusion  of  some  astringent  vegetable.  Oak  bark, 
from  its  cheapness,  and  the  quantity  of  tannin  it  contains,  is 
commonly  employed  in  the  preparation  of  leather,  both  in  this 
country,  and  in  Europe.  The  bark  of  the  hemlock  spruce, 
and  of  the  chesnut,  the  leaves  of  the  different  species  of  su- 
mach, and  various  other  astringent  vegetables,  are  used  in  sec- 
tions of  country  where  oak  is  scarce.  The  strength  of  the 
astringent  infusion  is  increased  from  time  to  time,  until  the 
skin  is  saturated  with  tannin.  A  portion  of  extractive  matter 
likewise  combines  with  the  hide,  and  to  this  the  brown  color, 
which  is  common  in  leather,  is  owing.  The  presence  of  this 
extractive  is  supposed  to  render  leather  more  tough  and  pliable. 

When  strong  or  saturated  solutions  of  tannin  are  used,  the 
leather  is  formed  in  a  much  shorter  time,  but  it  is  observed 
tliat  leather  tanned  in  this  way  is  more  rigid  and  more  liable  to 
crack,  than  that  made  in  the  common  manner,  with  weaker  in- 
fusions, gradually  increased  in  strength.  But  sole  leather,  the 
most  important  requisites  of  which  are  firmness  and  resistance 
to  water,  is  immersed  in  an  infusion  kept  nearly  saturated  by 
alternate  strata  of  bark.  The  full  impregnation  requires  from 
10  to  18  months. 

The  currying  of  leather  is  performed  by  covering  the  skin 
or  leather,  while  yet  moist,  with  common  oil,  which,  as  the 
moisture  evaporates,  penetrates  into  the  pores  of  the  skin,  giv- 
ing it  a  peculiar  suppleness,  and  rendering  it,  to  a  certain  ex- 
tent, water  proof.  During  the  process,  it  is  pared,  washed, 
and  rubbed,  to  increase  its  flexibility.  The  black  color  is  also 
imparted  by  the  currier,  by  rubbing  the  outside  with  a  solution 


468  ON  THE  PRESERVATION 

of  copperas,  or  any  solulion  of  iron,  which  immediately  turns 
it  black  by  combining  with  the  tannin  in  the  leather. 

Tawing,  is  the  method  by  which  skins  are  dressed  of  a 
white  color,  and  it  is  performed  without  the  use  of  bark.  The 
skins  are  first  prepared  by  steej)ing  them  in  lime  water,  and 
subjecting  them  to  various  processes  of  scraping  and  fulhng. 
They  are  then  fermented  with  wheat  bran,  and  afterwards 
impregnated  with  a  solution  of  alum  and  common  salt.  Be- 
fore being  dried,  they  are  fulled  with  wheat  bran  and  yolks  of 
eggs,  and  are  thoroughly  trodden,  steeped,  and  w^ashed.  In 
this  process,  the  place  of  tannin  appears  to  be  supplied  by 
some  principle  extracted  from  the  alum. 

As  examples  of  the  foregoing  processes,  common  sole 
leather  is  simply  tanned,  the  upper  leather  of  boots  and  shoes, 
is  tanned  and  curried,  the  white  leather  for  gloves  is  tawed,  and 
fine  morocco  leather  is  tawed,  and  afterwards  slightly  tanned 
with  sumach,  and  dyed.  Chamois,  and  other  kinds  of  wash 
leather,  are  steeped  in  lime  pits,  and  afterw^ards  fulled  with  oil. 
Before  the  dressing  is  finished,  the  superfluous  oil  is  scoured 
out  with  an  alkaline  liquor. 

Parchment. — Parchment  used  for  writing,  is  prepared  from 
the  skins  of  sheep  and  goats.  These,  after  being  steeped  in 
pits  impregnated  with  lime,  are  stretched  upon  frames  and  re- 
duced by  scraping  and  paring,  with  sharp  instruments.  Pul- 
verized chalk  is  rubbed  on  with  a  pumice  stone  resembling  a 
muller,  which  smooths  and  softens  the  skin  and  improves  its 
color.  After  it  is  reduced  to  something  less  than  half  its  orig- 
inal thickness,  it  is  smoothed  and  dried  for  use.  Vellum  is  a 
similar  substance  to  parchment,  made  from  the  skins  of  very 
young  calves. 

Catgut. — The  strings  of  certain  musical  instruments,  the 
cords  of  clock  weights,  and  those  of  some  other  machines  and 
implements,  are  made  of  a  dense,  strong,  animal  substance, 
among  us  usually  denominated  catgut.  It  is  derived  from  the 
intestines  of  different  quadrupeds,  particularly  those  of  cattle 
and  sheep.    The  manufacture  is  chiefly  carried  on  in  Italy  and 


OF  ORGANIC  SUBSTANCES. 


489 


France.  The  texture  from  which  it  is  made,  is  that  which 
anatomists  call  the  muscular  coat,  which  is  carefully  separated 
from  the  peritoneal  and  mucous  membranes.  After  a  tedious 
and  troublesome  process  of  steeping,  scouring,  fermenting,  in- 
flating, &z;c.,  the  material  is  twisted,  rubbed  with  horsehair 
cords,  fumigated  with  burning'  sulphur,  to  improve  its  color, 
and  dried.  Cords  of  different  size,  and  strength,  and  delicacy, 
are  obtained  from  different  domestic  animals.  The  intestine 
is  sometimes  cut  into  uniform  strips  with  an  instrument  made 
for  the  purpose.  To  prevent  offensive  effluvia  during  die 
process,  and  to  get  rid  of  the  oily  matter,  the  French  make 
use  of  an  alkaline  liquid  called  eau  de  Javelle. 

Gold  Beater^s  Skin. — This  delicate  membrane  is  also  man- 
ufactured from  the  intestines  of  animals.  The  workman  strips 
off  that  part  of  the  peritoneal  membrane  which  surrounds  the 
c(BCum.  He  then  takes  about  two  feet  of  it  in  length,  turns  it 
inside  out,  and  leaves  it  to  dry.  It  is  afterwards  steeped  in  a 
weak  solution  of  potash,  cleansed  by  scraping,  and  cut  open. 
It  is  then  stretched  to  dry  upon  wooden  frames,  and  notwith- 
standing the  tenuity  of  the  membrane  when  dry,  every  piece 
of  it  is  double  or  consists  of  two  membranes  glued  together. 
It  is  finished  by  washing  it  with  a  solution  of  alum,  and  coating 
it  with  isinglass  an'd  whites  of  eggs,  together  with  some  aromat- 
ics  to  repel  insects.  * 

Specimens  in  JVatural  flis^ori/.— Preparations  of  animals 
intended  to  show  their  external  form  and  characters,  are  made 
by  detaching  their  skins,  and  stuffing  or  mounting  these  so  as 
to  represent  the  natural  figure  and  attitudes  of  the  animal. 
Quadrupeds  and  birds,  are  preserved  by  extracting  the  body 
through  an  opening  on  the  under  side,  at  the  same  time  invert- 
ing the  skin.  The  fleshy  parts  of  the  limbs,  are  extracted 
through  the  same  opening,  also  the  neck,  brain,  and  eyes,  leav- 
ing the  skull,  if  the  animal  be  small.    Care  is  taken  not  to  in- 

*See  Franklin  Journal,  iil.  223,  and  London  Mechanics  Magazine,  vi.  63. 
alfio  the  Prize  Essay  of  Laharraque,  1822. 

62 


490 


ON  THE  PRESERVATION 


jure  the  hair,  or  plumage.  When  the  fleshy  parts  are  remov* 
ed,  the  inside  of  the  skin  is  rubbed  with  some  poisonous  sub- 
stance, usually  arsenic,  *  to  prevent  insects.  The  skin  is  then 
returned  to  its  natural  situation,  and  filled  with  cotton  or  tow, 
or  what  is  still  better,  an  artificial  body,  shaped  out  of  w^ood, 
cork,  or  dried  clay,  may  be  introduced  within  the  skin.  The 
opening  is  sewed  up,  and  wires  are  passed  longitudinally 
through  the  legs  and  neck.  These  are  afterwards  bent  into 
the  proper  position  to  give  the  attitude  desired.  Glass  eyes 
are  inserted,  and  the  hair  and  feathers  rendered  as  smooth  as 
possible,  and  retained,  while  drying,  in  paper  bandages. 

Reptiles,  and  fishes  without  scales,  are  extracted  by  careful- 
ly separating  the  bones  of  the  neck  through  an  opening  in  the 
throat,  or  gills,  and  inverting  the  skin.  In  serpents,  the  whole 
body  is  easily  extracted  through  the  mouth.  Fishes  with  scales 
cannot  be  turned  without  injury.  It  is  therefore  necessary  to 
detach  the  skin  carefully,  without  doubling  it.  Insects  may  be 
killed,  without  hurting  their  texture,  by  the  fumes  of  burning 
sulphur,  or  prussic  acid,  or,  in  many  cases,  by  pinching  the 
breast.  They  are  then  secured  by  pins,  and  placed  to  dry 
with  the  wings  and  legs  in  the  natural  attitudes.  Arsenic,  or 
corrosive  sublimate,  is  generally  necessary  to  secure  them  from 
the  depredations  of  other  insects. 

An  Herbarium,  or  collection  of  dried  plants,  is  usually  form- 
ed by  subjecting  the  plants,  while  fresh,  to  a  sufficient  pressure 
between  folds  of  paper,  to  preserve  their  natural  smoothness 
and  regularity,  until  they  become  dry.  The  plants  should  be 
gathered  at  a  time  when  their  characters  are  most  perfectly 
developed.  A  specimen  in  flower  should  be  preserved,  and  if 
possible,  one  also  in  fruit.  The  plant  must  be  carefully  spread 
out  on  smooth,  bibulous  paper,  so  that  the  leaves,  petals,  &ic., 
may  be  displayed  as  perfectly  as  possible.  In  this  situation  it 
is  retained,  and  another  sheet  of  paper  turned  gradually  over 

The  following  is  the  arsenical  soap  of  Becoeur,  much  used  in  France. 
Camphor,  5  ounces,  powdered  arsenic,  2  pounds,  whi(e  soap,  2  pounds,  salt  of 
tartar,  12  ounces,  lime  4  ounces,  melted  and  triturated  together. 


OF  ORGANIC  SUBSTANCES. 


491 


it,  commencing  at  one  side,  till  the  whole  is  covered.  Several 
sheets  of  paper  are  then  to  be  added  to  each  side,  and  the 
whole  placed  to  dry  under  a  strong,  equal  pressure.  In  this 
way  many  plants  may  be  preserved  without  further  trouble, 
especially  if  the  weather  be  warm  and  dry.  The  process, 
however,  may  be  expedited  by  shifting  the  papers,  or  by  pass- 
ing over  them  occasionally  a  warm  iron.  These  precautions 
are  more  necessary  for  succulent  plants,  or  for  others  in  cold 
and  damp  weather. 

Apperth  Process. — A  method  brought  into  notice  by  M. 
Appert,  for  preserving  articles  of  food  unchanged  for  several 
years,  deserves  to  be  noticed  among  the  practical  improvements 
of  the  present  century.  This  method  was  partially  known  at 
a  much  earlier  period,  but  its  most  successful  modes  of  appli- 
cation were  undoubtedly  discovered  by  M.  Appert.  It  con- 
sists in  a  very  simple  process.  The  articles  to  be  preserved 
are  inclosed  in  bottles,  which  are  filled  to  the  top  with  any  li- 
quid, for  example  with  the  water  in  which  the  article,  if  solid, 
has  been  boiled.  The  bottles  are  closely  corked,  and  cement- 
ed, to  render  them  hermetically  tight.  They  are  then  placed 
in  kettles  filled  with  cold  water,  and  subjected  to  heat  till  the 
water  boils.  After  the  boiling  temperature  has  been  kept  up 
for  a  considerable  time,  in  some  cases  an  hour,  but  varying 
with  the  character  of  the  article  to  be  preserved,  the  bottles 
are  suffered  to  cool  gradually.  In  this  state,  meats,  vegetables, 
fruits,  milk,  and  other  substances,  are  preserved  perfectly  fresh, 
without  any  condiments,  for  long  periods,  of  from  one  to  six  years. 
Instead  of  bottles,  tin  cannisters  are  sometimes  used,  and 
rendered  tight  by  soldering. 

The  remarkable  effect  of  this  process  has  been  explained, 
by  attributing  the  preservation  of  the  articles  to  the  total  ex- 
clusion of  atmospheric  air.  But  as  air,  in  common  cases,  is 
always  present  in  sufficient  quantities  to  excite  fermentation,  it 
is  supposed  that  the  application  of  heat  serves  to  fix  the  small 
portion  of  atmospheric  oxygen  which  is  present,  by  combining 
it  with  some  principle  in  the  other  substances  ;  so  that  it  is 


492     ON  THE  PRESERVATION  OF  ORGANIC  SUBSTANCES. 


no  longer  capable  of  producing  the  fermentative  action,  which 
in  parallel  cases  leads  to  decomposition. 


Chapman's  Treatise  on  the  Preservation  of  Timber,  8vo.  1817; — 
Tredgold's  Elementary  Principles  of  Carpentry,  4to.  IS^iO ; — Mc 
William,  on  the  Dry  Rot,  4to.  1818; — Article  Dry  Rot,  in  the  Sup- 
plement to  the  Encyclopedia  Britannica; — Aiken's  Chemical  Dic- 
tionary, article  Leather  ; — Labarraque,  VArt  du  Boyaudier;  Bulletin, 
de  la  Sociitt  de  V Encouragement  pour  V Industrie,  1822  ; — Letts om's 
Naturalist's  Companion,  8vo.  ; — Taxidermy,  or  the  Art  of  Collecting, 
Preparing,  and  Mounting  Specimens  in  Natural  History,  London, 
1823; — Appert,  Art  of  Preserving  Animal  and  Vegetable  Substan- 
ces, London,  translated,  1812; — Edinburgh  Review,  vol.  23,  p.  104. 


INDEX. 


Abutments,  120. 
Acanthus,  134. 
Achmet,  Mosque  of,  149. 
Acroteria,  129. 
Aerial  Perspective,  85. 
Aerostation,  225. 
Agate,  13. 
Agrigentum,  139. 
Air  flues,  165. 
Alabaster,  11. 
Alhambra,  151. 
Alloys,  387. 
Alloy  of  Gold,  391. 
Alternate  Motion,  237. 
Amalgam,  21. 
Amalgamation,  389. 
Amber,  23. 
Amianthus,  15. 
Amphiprostyle  Temple,  136. 
Amphitheatre,  143. 
Annealing,  392,  451. 
Animals,  Motion  of,  192. 
Animal  Power,  254. 
Anime,  434. 
Annotto,  443. 
Anthracite,  23. 
Anthracite  Grate,  162. 
Antimony,  22. 
Antiseptics,  478. 
Antae,  Temple  with,  136. 
Antoninus  and  Faustina,  144. 
Apollo  de  Belvidere,  8. 
Appert's  Process,  491. 


Apron,  258. 
Aqua  Tintai  96. 
Aqueducts,  212. 

 ,  302. 

Arabesque,  147. 
Araeo  Systyle,  146. 
Arbor,  note,  371. 
Arbor  Vitae,  31. 
Arcade,  121. 
Arch,  118. 
Archil,  442. 

Archimedes'  Screw,  310. 
Architecture,  114. 
Architrave,  128. 
Archivolt,  120. 
Argand  Lamp,  181. 
Arkwright,  Richard,  346. 
Arsenic,  22. 
Asbestus,  15. 
Ash,  26. 
Asphaltum,  23. 

 ,  429. 

Assaying,  387. 
Astragal,  129. 
Astral  Lamp,  178. 
Atmospheric  Engine,  283. 
Attic,  129.— Base,  134. 
Attrition,  332. 
Automaton  Lamp,  180. 
Axis,  note,  371. 
Axle,  note,  371. 
Axletrees,  200. 
Azure.    See  Ultramarine. 


494 


INDEX. 


Back  Water,  263. 
Badigeon,  431. 
Balance,  369. 
Balbec,  Temple  at,  146. 
Ballast,  220. 
Balloon,  225. 

Baltimore  Monument,  125. 

Band,  245. 

Band  Wheels,  229. 

Bark,  25. 

Bark  Mills,  334. 

Barker's  Mill,  266. 

Base  of  Columns,  128. 

Basilica,  143. 

Basis,  in  Dyeing,  440. 

Bass  Wood,  27. 

Batting,  347. 

Battlement,  148. 

Bay  Window,  148. 

Bayonets,  248. 

Beams,  Shape  of,  50. 

Beech,  27. 

Bell  Metal,  403. 

Belt  and  Segment,  244. 

Benzoin,  434. 

Besant's  Wheel,  264. 

Bevel  Gear,  232. 

Bice,  427. 

Biddery  Ware,  40^ 
Birch,  28. 

Birds,  Flying  of,  193. 
Biscuit,  471. 
Bismuth,  22. 
Bistre,  429. 
Bitumen,  23. 
Black  Lead,  24. 
Black  Walnut,  29. 
Blasting  with  Powder,  300. 
Bleaching,  438. 
Blowing  Glass,  451. 
Blue  Verditer,  426. 
Body  Colors,  426. 
Boiler,  227. 
Bole,  427. 

Bologna  Phials,  451. 
Boltels,  149. 


Bone,  39. 
Boring,  330. 

Boston  State  House,  125. 
Bottle  Glass,  452. 
Boustrophedon,  53. 
Boxwood,  32. 
Brake,  210. 
Brass,  20. 

 ,  400. 

Brazil  Wood,  442. 
Breast  Wheel,  265. 
Bricks,  463. 
Bridges,  204. 

Bridgewater's  Canal,  213. 
Broad  Glass,  452. 

 Wheels,  198. 

Bronze,  20. 

 ,  402. 

 Casting,  109. 

Brunswick  Green,  429. 
Brush  Wheel,  234. 
Buckets,  258. 
Buhrstone,  13. 
Bulk,  Limit  of,  48. 
Bunker  Hill  Monument,  10. 
Burning.  Pottery,  471. 
Burning  of  Smoke,  175. 
Burns'  Grate,  162, 
Bushnell's  Machine,  224. 
Butternut  Dye,  444. 
Buttons,  407. 
Buttonwood,  28. 
Buttress,  148. 
 ,  Flying,  150. 

Calamus,  58. 
Calcareous  Stones,  7. 
Caledonian  Canal,  215. 
Calico  Printing,  444. 
Cameos,  111. 
Cams,  237. 
Canals,  211. 

 ,  size  of,  215. 

Canal  Boats,  215. 
Candles,  177. 
Caoutchouc,  34. 


INDEX. 


495 


L/apiiais  01  L/Oiuinns,  i^o. 

v^iiroiuc  i\cu,  '±£ii. 

Capitol  at  Washington,  10. 

L/nrome  leiiow,  4^58. 

1  Ofi 

unurcn,  i4/. 

Kydl  dlS,  OVl. 

Cidpr  Mills  SS*! 

Parr!  Frirlo  ^/IQ 

\^liLUiaI  OaW,  OOu. 

L-araing,  o4o. 

Clay,  14. 

Carmine,  427. 

^-'lepsyui  a,  oou. 

L/arpeis,  od  / . 

Clock,  Description  of,  371i. 

Carthamus  Tinctorius,  428. 

Clock  w  orK,  COD. 

L/arioons,  4o^. 

i^iose  riauiea,  cvo. 

Cartwright's  Steam  Engine,  241. 

L/iose  ivooms,  i/o. 

Caryatides,  135. 

i^iuicnes,  ^4o. 

i^ase,  oi. 

L/Oai,  <so. 

Case  Hardening,  419. 

 Gas,  185. 

Casting,  341. 

 (jrrate,  Ibl. 

v-asi  iron,  4iu. 

ivOcnineai,  4^/,  44^. 

Casting  in  Plaster,  107. 

Cockle,  165. 

  Pottery,  470. 

Coiier  Dam,  205. 

Catenary  Arch,  119. 

  Walls,  117. 

Catgut,  488. 

Cohesion,  328. 

i^ainearai,  147,  lov. 

vyOin,  oyi. 

 ,  Milan,  125. 

Coining,  395. 

 ,  Strasburg,  125. 

Coin  Posts,  214. 

uavetto,  lou. 

i^oKe,  £16. 

Cedar,  30,  31. 

Coliseum  at  Rome,  124. 

\^un,  loo. 

\^01C0lIldr,  HlU  I  , 

\^OlUI  S,  oD. 

Cpmpntino-  3.^8 

Cnlniino-  fifi 

x^uiui ell  j-^iigi  uviiiy 0,  yo. 

I^OIOI  iVlIllS,  ooO. 

Chain  Piimn  5190 

Wl.  ^,^1  OCA 

L/Oiumn,  110,  izs. 

Chnlk  12 

cnamois  ijeainer,  4oo. 

Composite  Order,  142. 

Charcoal,  155. 

Compression,  44. 

Charring  of  Timber,  482. 

Concord,  Temple  of,  139. 

^uciiy  iree, 

Condensation  of  Steam,  274» 

VyIlcbilUr,  i  t . 

Condensing  Engine,  283. 

Cones,  Double,  235. 

Chill  Casting,  411. 

 ,  Geared,  235.1 

Chimnies,  167,  173. 

Constantine,  Arch  of,  145. 

China  Ware,  472. 

Contrast,  87. 

Chinese  Style,  132. 

Contrate  Wheel,  233. 

Chipolin,  432. 

Convoy,  210. 

Choir,  147. 

Copal,  434,  36. 

Choragic  Monument,  140,  141, 

Copper,  19. 

496 


INDEX. 


Copper,  Extraction  of.  399. 

 ,  Working  of,  399. 

 Plates,  90. 

Copperplate  Printing,  98. 
Copying  Machines,  59. 
Corbel,  149. 
Cordage,  344. 
Corinthian  Order,  134. 
Cork,  32. 
Cornelian,  13. 
Cornice,  128. 
Correcting  the  Press,  63. 
Corundum,  13. 
Cotton,  33. 

 Gin,  33. 

 Spinning,  346. 

Counterpanes,  358. 
Couplings,  247. 
Covering  of  Roofs,  127.- 
Cranks,  235,  239. 
Crayons,  430. 
Crevices,  169. 
Crochets,  148. 
Crocus  Martis,  427. 
Crown  Glass,  450. 

 Wheel,  233. 

Cross  Weaving,  355. 
Crucibles,  466. 
Crushing,  333. 
Crystallo  Ceramie,  460. 
Culverts,  212,  171. 
Cupellation,  389, 
Cupola,  121. 
Curb,  383. 

  Roof,  126. 

Currying,  487. 
Cutlery,  422. 
Cutting,  329. 

  Glass,  456. 

  Machines,  329. 

Cuttle  Fish  Liquor,  429. 
Cylinder  Glass,  453. 
Cymatium,  130. 
Cypress,  30. 

Danforth's  Speeder,  349. 


Davy's  Safety  Lamp,  188 
Dead  Water,  216. 
Decomposition,  476. 
Dentels,  134. 
Derbyshire  Spar,  12, 
Designing,  70. 
Devitrification,  459. 
Dial,  364. 

Diameter  of  a  Column,  130. 
Diamond,  13. 
Diastyle,  137. 
Die,  128. 

Diocletian's  Palace,  151. 
Dipteral  Temple,  136. 
Direction  of  Light,  83. 
Disengaging  Machinery,  241 
Dishing  Wheels,  199. 
Distemper,  431. 
Dividing  of  Bodies,  328: 
Diving  Bell,  222. 
Docking  of  Timber,  484. 
Dome,  121. 
Doric  Order,  133. 
Double  Fire  Place,  160. 
Double  Speeder,  349. 
Double  Weaving,  355. 
Dovetailing,  337. 
Drawing,  70,  130. 
Drawing  of  Cotton,  348. 
Dressing,  353. 
Drilling,  330. 
Drying  Oils,  36. 
Dry  Point,  91. 
Ductility,  43. 
Dutch  Pink,  428. 
Dyeing,  439. 
Dyes,  440. 

Ebony,  32. 
Echinus,  130,  133. 
Edge  Railway,  207. 
Egyptian  Style,  131. 
Elastic  Gum,  34. 
Elasticity,  43. 
Elastic  Moulds,  108. 
Elephanta,  131. 


INDEX. 


497 


Hiievaiion,  lou. 

r  iiicriiig  oloiic.    occ  r  rccsiuiic 

f  11 1>  JCfliglllCS,  0£iO* 

Flm  2fi 

^^^^^^  ill  Liic^  yjyjs^ii  ciii  , 

  A/TnHpQ  nf  Prnmrincr  IQO 

TrnVkOtilrmon^a  Oil 
HilUUallKIIlcIllSj  £il.Xt 

ITironlarPQ    1^7  179 

Frtiprv  13 

Firs,  30. 

"Fniimpllincr 
X-iliaXllclilll^)  '±L/0* 

f  ISllCO,  O  W  IXlllilliig  Ul,  XiJV 

E]nc3.ustic  Painting,  432. 

r  laKe  wniie,  4ou. 

jLincnasing,  oyi. 

r  lame,  i  /o. 

Engaging  Machinery,  247. 

r  lange,  /. 

HillglllCS,  JT  irc,  O^D. 

Flaab  WVipaI  ^'id 
r  idsii  ty  iicci,  o^o. 

Flat  Rnarrla  9fi9 

HiUgrdviiig,  yyj. 

JT  IdX,  uO. 

Engraving  of  Gems,  111. 

r  Unt,  liS. 

Hiniries,  loif. 

r  lint  ijriass,  40j. 

jiiniaDiaiure,  i^o. 

r  lue  Jjouers,  zio. 

iiiniasis,  110. 

JT  luor  spar,  i^. 

ii.picycioiaai  w  neei,  ^4iS. 

r  luxes,  o4i. 

xi,pisiyiium,  1^0. 

r  ly,  o74. 

Equalizing  Motion,  248. 

a  lying  ijurrressj  lou. 

Erectheum,  141. 

r  ly  w  neei,  zou. 

Hirie  uanai,  ^10. 

Forces,  Moving,  253. 

Essenay,  Temple  at,  149. 

Forcing  Pump,  314. 

i^tcnmg,  yo. 

Foreshortening,  72. 

Etruscan  Vases,  474. 

Forging,  412. 

Fnrt<!  499 

J^iApdUslUIl  JLiIlgillCS,  ^0  (  . 

X  Ul  111  Ul  lVXa.lcridla|  0\J» 

IT' vrioncinn  r\f  Sfpam  97fi 
JliXpalialULl  Ui  Olcd-Ili, 

V  UUUUallUilSy  XX'x* 

Extension,  43. 

Fountain  Lamp^  180. 

iiiXrraQos,  i^u. 

i:  UUUlalliS^  0^4. 

Eyes  of  a  Portrait,  85. 

1* ranKiort  £>iacK,  4^/. 

r  agaae,  izo. 

FrccstonCj  10, 

r  ast  uoiors,  44a. 

French  Berries^  443. 

r  ai  \Jii,  oo. 

J?  1  t^aCU  X  cllULlii^^  ^Oa» 

Feathers,  37. 

Friction,  251. 

Fecula,  36. 

Friction  of  Pipes,  305. 

Feeders,  211. 

Frieze,  or  Frize,  128. 

Feedpipe,  280. 

Fritting,  450. 

Feldspar,  9. 

Fuel,  153. 

Felling  of  Timber,  479. 

Fugitive  Colors,  446. 

Felting,  361, 

Fulling,  360. 

Fibres,  Combination  of  Flexible,  343.  Fur,  37. 

Field  of  Vision,  72. 

Furnaces,  163. 

Fig  Blue,  427. 

Fusee,  336. 

Fillet,  130. 

Fusible  Metal,  22. 

63 


498 


INDEX. 


FustiCj  443. 

Gothic  Style,  147. 

Governor,  248. 

Gable,  149. 

Granite,  8. 

Galena,  403. 

Graphite,  24. 

Galls,  444. 

Grate,  Anthracite,  162. 

Gamboge,  428. 

Graver,  91. 

Gangue,  385. 

Grecian  Style,  132. 

Gas  Engines,  294. 

  lemple,  loo. 

<jras  iiignis,  io4. 

vjrreco  Lrotnic  otjie,  i4o. 

ijrasmeter,  loo. 

(jrnnaing,  odo. 

ijrasometer,  loo. 

Grindstone.    See  Freestone. 

Gates,  213. 

Gristmill,  335. 

Gauze,  355. 

(jrroins,  I4y. 

Gear  Bevel,  232. 

Gudgeons,  note,  371. 

 ,  spiral,  Sol. 

txjm,  oD. 

Gearing,  230. 

 Tree,  29. 

Gelatin.    See  Glue. 

Gun  Making,  415. 

Gem  Engraving,  111. 

 Metal,  402. 

Gems,  Artmcial,  459. 

Gunpowder,  296. 

(jreneration  oi  fsteam,  ^274- 

<jrun,  r^roperties  oi,  /yy. 

Generator,  281. 

Guttae,  133. 

Gilding,  434. 

Gypsum,  11. 

 on  Metals,  oyo. 

 on  Porcelain,  474: 

Hackmatack,  31. 

Gin,  Cotton,  33. 

rlair,  o7. 

Glass,  449. 

 spring,  o70,  ool. 

 Blovring,  451. 

Halle  du  Bled,  122. 

 ,  rSroaa,  4o^. 

Hardness,  43. 

 ,  Crown,  4o0. 

Hargreaves,  Richard,  346. 

 Cutting,  456. 

Harmony,  87. 

 Cylinder,  453. 

Harnessing  of  Horses,  201 

 ,  I  lint,  4oi. 

Hanging  of  Pictures,  182. 

 ,  Plate,  4ao. 

rial  iviaKing,  ooi. 

 Shades,  183. 

rieart  v>  neel,  Soif. 

 ,  stained,  45b. 

rteaiing,  lOo. 

 Thread,  460. 

  by  steam,  loo. 

Glazing,  426. 

Heddles,  353. 

  Porcelain,  471. 

Hematine,  442. 

(jrlue,  ody,  4U. 

n.t5IIllUC14,  ov. 

Gold,  21,389. 

Hemp,  32. 

 Beater's  Skin,  489. 

Herbarium,  492. 

 Beating,  392. 

Herculaneum  Manuscripts,  56. 

 Leaf,  392. 

Herraopolis,  Temple  of,  10. 

Goldsmiths'  Work,  392. 

Hero's  Fountain,  322. 

Goldthread,  394. 

Hickory,  26. 

Gold  wire,  394. 

 Dye,  443. 

INDEX. 


499 


High  Steam,  293. 

  Pressure  Engine,  232, 

Highways,  202. 

IJindoo  Architecture,  131. 

Hipped  Roof,  126. 

History  of  Printing,  68. 

Hollow  Backs  of  Fireplaces,  160. 

Hcse,  13. 

Horizontal  Wheel,  265. 

 Wind  Mill,  268. 

Horn,  39. 

Hornbeam,  29. 

Hornblower's  Engine,  288. 

Horology,  364. 

Horses,  Attaching  of,  200. 

 ,  Power  of,  255. 

Hubb,  199. 

Hungarian  Machine,  321. 
Hydraulic  Cement,  16. 

 Ram,  323. 

Hydreole,  310. 
Hydrostatic  Lamp,  179. 

 Press,  316. 

Hypoethral  Temple,  137. 

Ichnographic  Projection,  80. 
^lissus,  Temple  on  the,  140. 
Illumination,  176. 
Imposing,  62. 
Impost,  120. 
Incipient  Fracture,  46. 
Inclined  Wheel,  242. 
Indellible  Ink,  59. 
India  Ink,  429. 
Indian  Red,  427. 
India  Rubber,  34. 
Indigo,  440. 

Induration  by  Heat,  463. 
Inertia,  194. 
Ink,  58. 

Ink,  Printers',  65. 
Inlaid  Work,  112. 
Insertion,  337. 

Instrumental  Perspective,  77. 
Intaglios,  112. 
Intercolumniation,  137 


Interposition,  337. 
Intrados,  120. 

Intrinsic  Color,  changing  of,  438. 
Invention  of  Letters,  53. 
Ionic  Order,  134. 
Iron,  488. 

 ,  19. 

Isinglass,  40. 

Isometrical  Perspective,  81. 
Ivory,  39. 
Ivory  Black,  429. 

Japanning,  434. 
Jasper,  13. 

Jenny,  Spinning,  346. 
Jewelling  Watches,  384. 

KaoHn,  472. 
Karnac,  150. 
Keel,  217. 
King  Posts,  126. 
King's  Yellow,  428. 
Knee  Joint,  247. 
Knives,  422. 

Lac,  36,  434. 
Lace,  356. 
Lacquering,  434. 
Lagarousse's  Lever,  246. 
Lakes,  427. 

Lambert's  Wheel,  264. 
Lamp  Black,  429. 
Lamps,  177. 

Lamp  without  Flame,  188. 

Lancet  Arch,  120. 

Languedoc  Canal,  215. 

Lanterns,  231,  147. 

Lantern  of  Demosthenes,  141. 

Lapis  Lazuli,  426. 

Larch,  31. 

Lateral  Strain,  45. 

Lathe,  331. 

Lead,  20. 

 ,  Extraction  of,  403. 

 Pipes  404. 

Leaning  Tower  at  Pisa,  125. 


• 


500 


INDEX. 


Leather,  486. 
Leaves  of  Pinions,  231. 
Lehigh  Coal,  23. 
Letters,  50. 
Lignum  Vitae,  32. 
Light  and  Shade,  82. 

 ,  Measurement  of,  183. 

 ,  Modes  of  Procuring,  190. 

Lightwood,  483. 

Limestone,  15. 

Limit  of  Bulk,  48. 

Line  Engraving,  91. 

Line  of  Traction,  197. 

Linens,  358. 

Lintel,  118. 

Lithography,  100. 

Litmus,  442. 

Locks,  338. 

Locks  of  Canals,  213. 

Locomotion,  192. 

Locomotive  Steam  Engine,  210. 

Locust,  26. 

Logwood,  442. 

Loom,  353. 

Luni  Marble,  8. 

Lustre  Ware,  474. 

Luxor,  150. 

Lysicrates,  Monument  of,  141. 

Machinery,  228. 
Machine  Printing,  67. 
Madder,  441. 
Magic  Porcelain,  475. 
Mahogany,  31. 
Maison  Carree,  144. 
Malleability,  42. 
Maltha,  18,  23. 
Manganese,  22. 
Man  Hole,  279. 
Maple,  28. 

 Dye,  444. 

Marble,  7. 

Marie  del  Fiore,  St,  123. 
Marseilles  Quilts,  355. 
Massicot,  428. 
Mastic,  36,  434. 


Materials,  estimation  of,  42. 
Materials  for  Writing,  54. 
Matrix,  385. 
Mc  Adam  Roads,  203. 
Measurement  of  Light,  183. 
Measures,  Architectural,  130, 
Mechanical  Lamp,  180. 

 Perspective,  79. 

Medals,  397. 
Melting  Glass,  450. 
Menai  Bridge,  205. 
Men,  Power  of,  254. 
Mercury,  21. 
Metallurgy,  385. 
Metals,  Extraction  of,  385. 
Metopes,  133. 
Mezzo  Tinto,  95. 
Mica,  9. 

Milan  Cathedral,  125. 
Mill,  Bark,  334. 

 ,  Barker's,  266. 

 ,  Cider,  335. 

 ,  Color,  336. 

 ,  Grist,  335. 

 ,  Stamping,  333. 

 ,  Sugar,  334. 

 ,  Oil,  334. 

 ,  Parent's,  266. 

 ,  Stone.    See  Buhrstone. 

Milling  of  Coins,  396. 
Mineral  Green,  429. 
Mineralizer,  385. 
Minaret,  147. 
Minerva,  Temple  of,  140. 

 ,  Polias  Temple  of,  14L 

Minute  Architectural,  130. 
Modelling,  106. 
Modillions,  135. 
Module,  130. 
Monopteral  Temple,  137. 
Moody's  Machines,  352. 
Moorish  Arch,  120. 
Mordants,  440. 
Mortar,  15. 

Motion  of  Animals,  192. 
Morey's  Engine,  290. 


INDEX. 


501 


Mortise,  127. 
Mortising,  337. 
Mosaic,  112. 

Moscow,  Riding  House  at,  126. 
Mosque  of  Achmet,  149. 

 of  St  Sophia,  124. 

Moulding  Glass,  455. 
Mouldings,  129. 
Moulds,  342. 

  for  Casting,  108. 

Moving  Forces,  253. 
Mule  Spinning,  351. 
Mullions,  148. 
Mutules,  133. 

Mylassa,  Sepulchre  at,  145. 

Nailing,  337. 
Nail  Making,  415. 
Naples  Yellow,  428. 
Naptha,  23. 

Natural  History,  Specimens  in, 
Nave,  199,  147. 
Needles,  423. 
Newcomen's  Engine,  283. 
New  York  Canal,  216. 

 City  Hall,  125. 

Nicaragua  Wood,  442. 
Nismes,  Temple  at,  144. 
Noncondensing  Engine,  282. 
Noria,  310. 
Novaculite,  13. 

Oak,  25. 
Obelisk,  124. 
Obelisks,  10. 

Obstruction  of  Pipes,  306. 
Ochres,  427. 
Ogee,  130. 

 Arch,  120. 

Ogyve,  149. 

Oil  Gas,  187. 

Oils,  34. 

Oil  Mill,  334. 

—  Painting,  432. 

Opus  Reticulatum,  112. 

Orchestra,  138. 


Orders  of  Architecture,  133. 
Ores,  385. 
Oriel,  149. 
Orpiment,  428. 
Orthographic  Projection,  80. 
Overshot  Wheel,  257. 
Ovolo,  129. 
Oxgall,  429. 

Paddle  Wheels,  221. 
Paestum,  138. 
Pagodas,  132. 
Painting,  71,  425. 

 in  Distemper,  431. 

 in  Fresco,  432. 

 in  Oil,  432. 

Paints,  426. 
Pak  Fong,  403. 
Pallets,  380,  244. 
Palmer's  Rail  Way,  208. 
489.  Palmyra,  Temple  at,  145. 
Pandroseum,  141. 
Panoramic  Views,  72. 
Pantheon  at  Rome,  124,  144. 
Paper,  57. 
Papermaking,  361. 
Pappenheim  Limestone,  8. 
Papyrus,  55. 
Parachute,  226. 
Parallel  Motion,  240,  290. 
Parapet,  148. 
Parent's  Mill,  266. 
Parchment,  57,  488. 
Parthenon  at  Athens,  140. 
Parting  of  Metals,  390. 
Party  Gold,  393. 
Passings,  209. 

Patent  Mineral  Yellow,  428- 
Pavements,  202. 
Peachwood,  442. 
Pearl,  White,  430. 
Peat,  24. 
Pedestal,  128. 
Pediment,  129. 
Penetration,  330. 
Pencils,  Black  Lead,  24. 


502 


INDEX. 


Pendentives,  122,  149. 
Pendulum,  368. 
Pendulum  Spring,  370,  383. 
Pentelic  Marble,  8. 
Pent  Roof,  126. 
Pepperidge,  27. 
Peripteral  Temple,  136,  137. 
Perkins'  Generator,  281 
Perkins'  Lock,  338. 
Perpetual  Screw,  233. 
Persian  Wheel,  309. 
Persepolis,  150. 
Perspective,  70. 
Perspectographs,  79. 
Petersburgh,  Columns  at,  9. 
Peter  the  Great,  Statue  of,  9. 
Petroleum,  23. 
Persimmon,  29. 
Petuntze,  472. 
Pewter,  20. 

Philadelphia  U.  S.  Bank,  125. 
PhcEnicin,  441. 
Phosphorus,  41. 
Picker,  347. 

Pictures,  Hanging  of,  182. 

Pilaster,  128. 

Pillar,  149. 

Pine,  29. 

Pinchbeck,  400. 

Pinion,  231. 

Pin  Making,  401. 

Pinnacles,  148. 

Pipes  for  Water,  303. 

Pisa,  Leaning  Tower  at,  125. 

Pise,  Building  in,  117,  118. 

Piston,  289. 

Pitch,  34. 

 Lines,  231. 

Pivots,  note,  371. 
Place  of  Strain,  46, 
Plan,  130. 
Plate  Glass,  45^. 
Plaster,  Casting  in,  107.  , 
Plaster  of  Paris,  11. 
Platinum,  22. 
Plating,  397. 


Plinth,  128. 
Plumbago,  24. 
Plying,  348. 
Pola,  Temple  at,  145. 
Polishing,  434. 

 Glass,  454. 

 Slate,  14. 

 Steel,  423. 

Pompey's  Pillar,  9. 
Porcelain,  472,  473. 

 ,  Magic,  474. 

Porphyry,  12. 
Portable  Gas  Light,  188. 
Portland  Stone,  8. 
Portland  Vase,  474. 
Portrait,  Eyes  of,  85. 
Posticus,  135. 
Pottery,  466. 

Power,  Maintaining,  367, 
Powers,  Moving,  253. 
Precious  Stones,  13. 
Preservation  of  Food,  491. 

 of  Organic  Substances, 

478. 

Press,  Correction  of,  63. 

 ,  Hydrostatic,  316. 

 ,  Printing,  65. 

Pressing  Glass,  455. 
Printing,  59,  66. 

 Porcelain,  471. 

 Press,  65. 

Projections,  80. 

Projection  of  Water,  324. 

Pronaos,  135. 

Propyloea  at  Athens,  139. 

Proscenium,  138. 

Prostyle  Temple,  136. 

Prussian  Blue,  426. 

Pseudo  Dipteral  Temple,  137. 

Puddle,  212. 

Puddling  Furnace,  412. 

Pulley,  Live  and  Dead,  248. 

Pulpit,  138. 

Pumice,  14. 

Pump  Bag,  317. 

 ,  Centrifugal,  313. 


INEEX. 


603 


Pump  Chain,  320. 

 ,  Common,  314. 

 ,  Delahire's,  316. 

 ,  Double  Acting,  318. 

 ,  Eccentric,  319,  320. 

 ,  Forcing,  314. 

 ,  Lifting,  317. 

 ,  Plunger,  315. 

 ,  Rolling,  318. 

  Rope,  310. 

 ,  Spiral,  311. 

 ,  Sucking,  314. 

Puppet  Valve,  288. 
Puteolanus  Pulvis,  16. 
Putty,  21,  339. 
Puzzolana,  16. 
Pycnostyle,  note,  137. 
Pyramid  of  Egypt,  124. 
Pyramids,  8. 

Quadrupeds,  Motion  of,  192. 
Quartation,  390. 
Quartz,  9. 
Queen  Posts,  126. 
Quercitron,  443. 
Quicklime,  15. 
Quills,  37. 
Quincy  Stone, 

Rabating,  337. 
Rack,  246. 

Rack  and  Pinion,  243. 

  and  Segment,  243. 

Radius,  231. 
Rafters,  126. 
Rag  Wheels,  230. 
Rail  Roads,  206. 
Rampart  Arch,  120. 
Ratchet  Wheel,  234. 
Reaumur's  Porcelain,  459. 
Reciprocating  Motion,  237. 
Rectilinear  Motion,  245. 
Red  Cedar,  31. 
Red  Lead,  427. 
Reduction  of  Metals,  386. 
Reeded  Column,  151. 


Reflected  Light,  84. 
Reflectors,  182. 
Refractory  Clay,  14. 
Resilience,  43,  46. 
Resins,  36. 
Resistance,  43. 
Restorations,  130. 
Retention  of  Heat,  168. 
Reticulated  Walls,  117. 
Rhode  Island  Coal,  23. 
Rhus  Copallinum,  434. 

 Vernix,  434. 

Rice  Paper,  note,  55. 

Rivets,  338. 

Roads,  202. 

Roasting  Ores,  386. 

Rocou,  443. 

Rollers,  196. 

Rolling  Iron,  412. 

Roman  Cement,  16. 

Roman,  Doric,  and  Ionic,  142. 

Romanesque  Architecture,  146. 

Roof,  125. 

Rope  Making,  344. 

Rope  Pump,  310. 

Rose  Wood,  32. 

Rosin,  34. 

Rotary  Motion,  229. 
Rotten  Stone,  14. 
Rouge,  428. 

Rouge  d'  Angleterre,  427 

Roving,  349. 

Rubble  Walls,  117. 

Ruby,  13. 

Rudder,  217. 

Rumford  Fireplace,  159- 

Rupert's  Drops,  451. 

Safety  Gates,  213. 

 Lamp,  188. 

 Valve,  280. 

Saffron,  443. 
Safflower,  443. 
Saggars,  471. 
Sand,  14. 
Sandarac,  434. 


604 


INDEX. 


Sand  Stone,  10. 
Salona,  Temple  at,  146. 
Sap  Green,  429. 
Sappan  Wood,  442. 
Sapphire,  13. 
Saracenic  Style,  147. 
Satin  Wood,  32. 
Sawing,  332. 
Saw  Mill,  332. 
Saws,  422. 

Savannah  Steam  Ship,  222. 
Saxon  Architecture,  146. 
Scagliola,  112. 
Scapements,  244,  370. 
Scarfing,  127,  337. 
Scenographic  Projection,  80. 
Schemnitz  Vessels,  321. 
Schuylkill  Bridge,  205. 
Scissors,  420. 
Scoop  Wheel,  309. 
Scotia,  130. 
Screwing,  337. 
Screw,  Archimedes,  310. 

 ,  Perpetual,  233. 

Sculpture,  106,  109. 
Sealing  Wax,  339. 
Seasoning  of  Timber,  480. 
Section,  130, 
Sepia,  429. 
Serpentine,  11. 
Serpents,  Motion  of,  193. 
Shades,  87. 
Shades,  Glass,  183. 
Shadows,  85. 
Shaft,  note,  371. 

 of  Columns,  128. 

Shafts,  212. 

Shape  of  Timber,  48. 

Shearing,  360. 

Sheet  Lead,  414. 

Shell  Lac,  See  Lac,  434. 

 Gold,  434. 

Shot,  Leaden,  405. 
Sidelings,  209. 
Sienna,  Burnt,  428. 
 ,  Terra  di,  428. 


Sienite,  9. 
Signatures,  63. 
Silk,  38. 
Silver,  21. 

 ,  Extraction  of,  394. 

Silvering  of  Mirrors,  407. 
Silver  Edges,  398. 
Silversmiths'  Work,  395. 
Singeing,  358. 
Sinkicien,  Pagoda  at,  149. 
Single  Rail,  208. 
Sinumbral  Lamp,  183, 
Size,  40. 

Size  of  Wheels,  196. 
Skins,  37. 
Skylights,  169. 
Slaking  of  Lime,  15. 
Slate,  10. 
Slitting,  415. 
Smalt,  427. 
Smelting,  386. 

 ,  408; 

Smoke,  Burning  of,  175. 
Smoky  Rooms,  171. 
Snail,  374. 
Soap  Stone,  10. 
Soldering,  340. 
Sources  of  Power,  253. 
Spalatro,  Temple  at,  146. 
Spandrells,  148. 
Span  of  an  Arch,  120. 
Speculum  Metal,  402. 
Spelter,  22. 
Spinning,  346,  351. 
Spiral  Gear,  231. 
Spiral  Pump,  311. 
Splicing,  127. 
Spire,  147. 
Springs,  200. 
Spruce,  30. 

Stability  of  a  Ship,  220. 
Stamping  Mill,  333. 
Stained  Glass,  456. 
Starch,  36. 
Steam,  270. 
  Boats,  220. 


INDEX. 


505 


Stea.ni  Cavriages,  29o. 

— — —  hiUgme,  /i4  4 ,  401. 

oypnun,  ouo. 

— —  Engine,  History  of,  201 , 

oysiyie,  lo/. 

Tnlnn  130 

T-Tpjltinrr  Vnr    1  fif ^ 

Fanning,  486. 

  Power,  270. 

Tapestry,  357. 

Steel,  19. 

Tar,  34. 

 ,  417. 

Tarras,  17. 

  Engraving,  99. 

Taunton  Spindle.    See  Danforth. 

Steeple,  147. 

Tawing,  488. 

Stereotyping,  66. 

Teazle,  360. 

Stiffness,  43. 

Teeth  of  Wheels,  230. 

St  Genevieve's  Church,  Paris,  123.  Telford's  Road,  203. 

otippung,  yo. 

Tempering,  419. 

ot  iviarie  aei  r  lore,  \.4io- 

J. empic  oi  V  csid,  ctL  xivuii, 

ot  MarK  s  L/liurca,  Venice,  l44. 

1  enacity, 

atone  ±>lue,  4.4/. 

1  ents,  urigiii  oi,  v^iuntst  Ksiyit, 

OtUill:/b,  J-ii tilU^l dpilio ,  JvX. 

132. 

otone  ware,  4do. 

1  erra  v-zoiia,  'ioo. 

oloves,  lOo. 

— — —  veriB,  'i.AiJ. 

St  Paul's  T^nndon  123 

Thpatrfi   fi-rpoian  137 

St  Peter's,  Rome,  123. 

Thebes,  Ruins  of,  150. 

Strasburg  Cathedral,  125. 

Theodori,  Tomb  of,  8. 

Strain,  42. 

ThermcB*  143. 

Strength,  43,  46. 

Theseus,  Arch  of,  145. 

 of  Materials,  42. 

,  Temple  of,  139. 

Stress,  42. 

Thrasyllus,  Monument  of,  140. 

Striking  Part  of  a  Clock,  373. 

Throttle  Valve,  289. 

St  Sophia,  Mosque  of,  124. 

Throwing,  470. 

Stucco,  11. 

Throwing  Wheel,  326. 

Stylobate,  128. 

Tie  Beam,  126. 

Stylus,  54,  58. 

Tiles,  465. 

Styles  of  Building,  1Q7. 

Timber,  479. 

Sublimation,  342. 

Tin,  20,  406. 

Submarine  Navigation,  224. 

Tinfoil,  406. 

Sugar  Mill,  334. 

Tin  Plates,  406. 

Sulphur,  24. 

Toggle  Joint,  247. 

Sun  Dial,  364. 

Tombac,  400. 

Sun  and  Planet  Wheel,  241. 

Tone,  87. 

Surbase,  128, 

Tongueing,  337. 

Suspension  Bridges,  205. 

Toothed  Wheels,  230, 

Swell  of  Columns,  116. 

Tophus,  8. 

Swimming,  194. 

Torches,  177. 

Bladder  of  Fish,  193     Torpedo,  225. 
64 


506 


INDEX. 


Torsion,  48. 
Tortoise  Shell,  39. 
Torus,  129. 
Tower,  148. 

Tower  of  the  Winds,  141,  364. 
Tracery,  149. 
Tracing  Paper,  92. 
Traction,  lijie  of,  197. 
Trajan's  Column,  124. 
Tram  Road,  208. 
Transept,  147. 
Transparent  Colors,  426. 
Transparency  of  Flame,  183. 
Travertine,  8. 

Treadwell  on  Rail  Roads,  209- 
Triglyphs,  133. 
Tripoli,  14. 

Triumphal  Arches,  143. 
Trundle  231. 
Trussing,  126. 
Tubes,  46. 
Tulip  Tree,  27. 
Tunnels,  212. 
Tupelo,  29. 
Turmeric,  443. 
Turncap,  174. 
Turning,  331. 
Turnsol,  442. 
Turpeth  Mineral,  428. 
Turpentine,  34. 
Turret,  148. 
Tuscan  Order,  142. 
Twilling,  354. 
Twisted  Column,  151. 
Twisting,  Theory  of,  343- 
Tympanum,  129. 
Types,  60,  61. 

Ultramarine,  426. 
Umber,  429. 
Undershot  Wheel,  261. 
Union,  Modes  of,  337. 
Universal  Joint,  233. 
 Lever,  246. 

Valves  of  Canals,  214. 


Valves  of  Steam  Engines,  288. 

Vanishing  Point,  75. 

Vapors  of  Low  Temperature,  294. 

Varnishing,  433. 

Vases,  Etruscan,  474. 

Vaults,  121,  149. 

Vehicles  of  Power,  253- 

Vellum,  488. 

Velocity,  Change  of,  235. 
Velvets,  358. 
Venetian  Red,  427. 
Ventilation,  170. 
Ventilators,  171. 
Venus  de  Medici,  8. 
Verandah,  132. 
Verdigris,  423. 
Vermillion,  427. 
Vesta,  Temple  of,  145. 

 ,  Temple  of,  at  Tivoli,  124. 

Vitrification,  448. 
Volutes,  134. 
Voussoirs,  120- 

Wall,  116. 
Walnut,  26,  29. 
Wafers,  339. 
Warping,  352. 
Washing  Ores,  386. 
Washington,  Capitol  at,  125. 
Watch,  Description  of,  376. ' 
Water  Cements,  16. 

 Clock,  366. 

 Colors,  431. 

 ,  Conveying  of,  302. 

 in  Fuel,  154. 

 Pipes,  303. 

 Power,  257. 

 ,  Raising  of,  308. 

 Snail,  311. 

Watt's  Steam  Engine,  284. 
Wax,  41. 

 Sealing,  339. 

Weaving,  353. 
Wedgewood's  Ware,  468. 
Weight  of  Fuel,  153. 
Weirs,  213. 


INDEX, 


507 


vv  eiu J  'i'io. 

Whifp  WnnH  27 

TT  llllO     TT  UUU,   <W#  , 

Wpldino*  340 

Whitincr  430 

Westminster  Abbey,  150. 

See  Chalk 

TT  lllOVV,  OA. 

WinHno-p  9QQ 

Wheel,  Besant's,  264. 

Wind  Fflert  of  on  Sails  218 

»T  inurniiis,  /suc. 

Brush  "31 

Windows  170 

W\nf\  Pnwpr  9^7 

VV  ipers,  4ov- 

 ,  uonirate,  doo. 

Wire  Drawing,  41-0. 

 5  l^rown,  /500. 

w  oaa,  441. 

 ,  Jiipicj-cioidai,  4^4- 

vv  ooa,  ^0. 

 ,  r  lasn,  o4o. 

w  ooden  xsnages,  .^ui. 

 ,  llorizontai,  Jsoo. 

Wood  Engravings,  99. 

VV  ool,  oo. 

 ,  JLamDeri  s,  ^404. 

wooii  s  Jiingme,  4,oo- 

,  LfVersnoi,  4,04. 

woollens,  ooy. 

,  ivaicneij  i^o't. 

VV  orm,  /ioo. 

Thro  win  0"  3% 

Worsted,  359. 

 ,  Undershot,  261. 

 ,  Window,  149. 

Yellow  Ochre,  428. 

Wheels,  Form  of,  199. 

Whetstone.    See  Novaculite. 

Zinc,  22. 

White  Cedar,  30,  31. 

 ,  White,  430. 

 Lead,  430. 

Zophorus,  128. 

 Pigments,  430. 

Zurich  Machine,  312. 

Ware,  468. 


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STRENGTH  OF  MATERIALS. 


Plati:  XII 


Fig.  1. 


1 


LOCOMOTION. 


MACHINERY.  Platk  XIV. 


LOCOMOTION. 


Plate  XV. 


Fig.  3. 


MACHINERY. 


Plat*  XVf. 


a. 


7 


IL 


MACHINERY. 


Platk  XVII. 


Pig.  24.  Fig.  25.      Fig.  26.  Fig.  27. 


Pig.  28.  Fig.  31.  Fig.  30. 


MACHINERY. 


MOVING  FORCES.  Plate  XVIII. 


MOVING  FORCES. 


Plati:  XIX 


Fig.  6. 


CONVEYING  WATER.  Plate  XXI. 

Fig.  8. 


Fig.  13.  Fig.  14.  Fig.  15. 


WATER.        FLEXIBLE  FIBRES.       HOROLOGY.       Plate  XXH. 

Fig.  18. 


Fig.  4. 
Fig.  5. 


Fig.  L 


r 


